The Fruticose Species of Usnea Subgenus Usnea in East Africa

Lichenologist 11(3): 207-252 (1979) 

THE FRUTICOSE SPECIES OF USNEA SUBGENUS 

USNEA IN EAST AFRICA 

T. D. V. SWINSCOW* and HILDUR KROGf 

Introduction 

The plants considered in this paper belong to the fruticose species of Usnea Wigg. 

em. Ach. subgenus Usnea found in East Africa. They comprise 15 species that we 

have not previously discussed,here considered in detail,and two aggregates which 

have been the subject of previous papers, namely, the corticolous U. undulata 

aggregate (Swinscow and Krog, 1975) and the saxicolous U. bornmuelleri aggregate 

(Swinscow and Krog, 1976a). Short additions or amendments are made to the 

previous accounts of these aggregates, and the species in them are incorporated in 

the key to the East African fruticose Usneae. 

Earlier important collections, though mostly small, have been made of this group 

in East Africa by Schimper (see Motyka, 1936-38), Meyer (Stein, 1888), von 

Liechtenstein and Pospischill (Steiner, 1897), Pichi-Sermolli (Motyka, 1952), 

Stauffer (Motyka, 1959), Maas Geesteranus (Motyka, 1961), and Schutz (Bertsch, 

1962). Stizenberger (1890-91) reported on specimens collected by Hildebrandt and 

others, and Dodge (1956, 1957) on specimens deposited at K and EA. These and 

other authors have described new species, varieties, and forms that include East 

African material, but considerable taxonomic problems remain. 

In the first part of the paper we describe the morphological and chemical characters 

found in the corticolous fruticose species and discuss their value in the delimitation 

of the species. And we anticipate the conclusions by referring for convenience 

to the species as we have come to understand them from the study reported here. 

In the second part we provide a key to the species and report on each individually. 

Materials and Methods 

The main collections of specimens used in this study are those made by the authors in 

Uganda (T.D.V.S. 1969, 1970, 1971), southern Ethiopia (H.K. 1972), Kenya (H.K. and 

T.D.V.S. 1972, 1973, 1974, H.K. 1976, T.D.V.S. 1977), and northern Tanzania (H.K. and 

T.D.V.S. 1974); Lye in Uganda (1969-71); and Tapper in Ethiopia (1971, 1972). In addition 

we have received specimens from other collectors whose loans are gratefully acknowledged at 

the end of the paper and examined specimens deposited by various collectors in institutional 

herbaria. Specimens cited with a number but without a collector's name were collected by the 

authors; all others are cited with the collector's name. Representative specimens have been 

deposited in BM, O and East African herbaria. Many type specimens have also been examined, 

and their chemistry is recorded below. Synonyms are included only when they represent new 

information, except that basionyms are included. 

Chemical data were obtained by thin-layer chromatography (t.l.c.) with the techniques 

described by Culberson and Kristinsson (1970) and Culberson (1972), modified by Menlove 

(1974). Microcrystal tests were performed with conventional reagents when necessary. 

* 24 Monmouth Street, Topsham, Exeter EX3 OAJ. 

t Botanical Museum, University of Oslo, Trondheimsveien 23 B, Oslo 5, Norway. 

0024-2829/79/030207-r 46 $02.00/0 

© 1979 British Lichen Society

208 THE LICHENOLOGIST Vol. 11 

Characters of Taxonomic Importance 

Owing to their saxicolous habitat as well as their stiff cartilaginous branches the three 

species in the Usnea bornmuelleri aggregate could not be confused with the corticolous 

species. They are therefore not considered further in the differentiation of the 

corticolous species, which is discussed below in the first part of the paper. 

A variety of characters were examined to identify those which could be used for 

the discrimination of the corticolous species. The following were found to be of 

value: nature of propagules; mode of branching; shape of branches in cross and 

longitudinal section; frequency of spinules and fibrils; presence or absence of papillae, 

tubercles, and pseudocyphellae; thickness of cortex; presence and distribution 

of pigment; and chemistry. Blackening at the thalline base was occasionally of some 

discriminatory value. These characters are considered individually below. Characters 

found to be of little or no value in the delimitation of species included coloration 

of the thallus on herbarium storage; density of medulla; width of medulla and 

axis; and morphology of ascocarps, ascospores, pycnidia, and conidia. In all species 

for which they were seen the ascospores were simple (or a few had pseudosepta) and 

broadly ellipsoid, 8-12 (-15) x 5-8 urn. The conidia were as illustrated for Usnea 

articulata (Swinscow and Krog, 19766), that is, rod-like with a swelling near the 

lower end and 7-10 urn long. 

Propagules 

The species could be divided initially into two main groups, namely, primary 

species usually producing numerous apothecia and lacking isidia and soralia 

(though a few isidia may occasionally be seen), and secondary species producing 

numerous isidia or soralia or both. Isidia might be produced in pseudocyphellae or 

on the cortex, and were differentiated from spinules by the absence of an axis. 

Soralia might be primary, or they might develop secondarily from pseudocyphellae. 

A group of species was characterized by the production of primary soralia, and these 

were often excavate initially, though they might become protuberant as they 

developed. In this group no or very few isidia were produced. Soralia secondary to 

pseudocyphellae were usually protuberant. 

Mode of branching 

Branches are usually formed by isotomic dichotomy, so that they mostly diverge 

at an acute angle and lie alongside each other. But in some thalli many branches had 

developed as lateral outgrowths, and these in turn gave rise to more lateral branches, 

so that many were at right angles to each other. 

Shape of branches 

In cross-section the main branches are usually more or less circular, but in some 

species many were angulate. In longitudinal section branches are usually tapered, so 

that they gradually decrease in diameter from base to apex, but in some species they 

were fusiform. 

Spinules and fibrils 

These are laterally developed appendages containing an axis as well as medulla. 

Appendages up to about 3 mm long are regarded as spinules, longer as fibrils.

1979 Usnea in East Africa—Swinscow & Krog 209 

Though the distinction is arbitrary, it is useful in practice (Swinscow and Krog, 

1978). Fibrils, which grow to about 1 cm, often seem to have developed from 

spinules; thus some spinules remain as such, while others grow on to become 

fibrils. The frequency of spinules was found to vary inversely with that of tubercles 

and papillae. This relationship was used to differentiate the Usnea complanata and 

U. submollis aggregates. 

Papillae, tubercles and pseudocyphellae 

These are closely related structures in Usnea. Papillae are hemispherical, conical, 

or cylindrical protuberances composed mainly of cortex. Tubercles are commonly 

larger, always contain medullary tissue connecting with the medulla of the branch, 

and when mature terminate with a pseudocyphella. Pseudocyphellae may be 

plane on the cortex, or slightly protuberant on the surface of the branch, or they 

may be (and more often are) at the apex of tubercles. Gaps in the cortex left on the 

branch after the breaking away of a spinule or branchlet sometimes resemble 

pseudocyphellae and may possibly serve the same function. 

Thickness of cortex 

This character was difficult to measure with sufficient precision to be of practical 

use, but it was found to be of help in discriminating Usnea picta. 

Pigmentation 

In some species the thallus contains an ochraceous to red pigment. In one species, 

Usnea roseola, the pigment was pink, like strawberry ice cream. The position of the 

pigment in the thallus was an important character: it was restricted to the cortex in 

some species, in others lay just under the cortex in the medulla (in the apothecia as 

well as in the branches), and in U. roseola was in the medulla adjacent to the axis. 

Some species were blackened at the base near the holdfast. As a discriminatory 

character this was generally of low value owing to lack of correlation with other 

characters, but it was occasionally used. 

The discoloration of the thallus that often accompanies ageing in the herbarium 

as well as being an unsatisfactory character in itself was sometimes found to obscure 

or mimic true pigmentation. 

In fresh material, while pigment is usually seen readily enough, it is occasionally 

so sparse as to be difficult to detect. Only a single patch may be found in the entire 

thallus. From this is a short step to specimens that lack pigment but belong to a 

species that is characterized by its presence. For example, occasional specimens 

lacking pigment have been tentatively assigned to the normally pigmented Usnea 

subflorida if they contained protocetraric acid, were morphologically concordant 

with that species, and were growing on twigs in montane forest (the usual habitat 

for it) with other thalli containing pigment. It is possible that the few specimens 

producing protocetraric acid and assigned to U. undulata owing to a lack of pigment 

(Swinscow and Krog, 1975) should be regarded as non-pigmented variants of U. 

sorediosula; but as a gradation of pigmentation down to an unpigmented state has 

not been seen in U. sorediosula we retain them at present in U. undulata. 

However, a re-examination of our collections of Usnea bornmuelleri and U. 

maculata (Swinscow and Krog, 1976a) has shown that a few specimens should be 

transferred from the first to the second species (see below under U. maculata).


Chemistry 

Closely related depsidones were the main substances produced by the great 

majority of specimens of all the fruticose species found in East Africa. Salazinic 

acid was the main or accessory substance in at least some races of most species. 

Stictic, norstictic, and constictic acids were much less common but were also 

widespread throughout the species. None of these alone provided useful taxonomic 

characters. 

In contrast, several chemical-morphological or chemical-pigmentary combinations 

were characteristic of particular species. For example, alectorialic acid, which 

was present in nearly all specimens of Usnea bicolorata, was in the soralia only 

(Pd+yellow). In the primary species U. submollis the alectorialic acid found in most 

specimens was restricted to the apothecia. The barbatic acid found in nearly all 

specimens of U. subflorida and one specimen of U. submollis was also in the apothecia 

only. The combination of protocetraric acid with a subcortical red pigment was 

found in all three main groups of species, being characteristic of U. subflorida in the 

primary group, U. sorediosula in the isidiate group, and U. bicolorata in the sorediate 

group. This chemical-pigmentary concordance may reflect a genetic connection 

between a primary species and two secondary species derived from it (see below). 

During chromatography an undetermined substance which became pink on 

exposure to sulphuric acid was found in a number of morphotypes, mostly those 

assigned to the newly described Usnea nodulosa and its unnamed isidiate counterpart 

(2U 16/10), but occasionally also in the U. complanata aggregate and in U. 

perplexans, associated in both with salazinic acid. It is referred to below as the 'pink 

unknown' substance. A pale yellow pigment was also found by t.l.c. in two specimens 

of U. submollis associated with salazinic acid, though it did not cause evident 

coloration of the thallus. 

Collections of Usnea complanata and U. submollis aggregates from three localities 

contained the combination galbinic, norstictic, and sometimes a trace of salazinic 

acid, which is highly characteristic of the isidiate species U. undulata. 

Fatty acids were found in occasional specimens throughout these collections but 

were particularly characteristic of Usnea subeciliata. Squamatic acid was occasionally 

found. In one specimen of U. ruwenzoriana it was associated with alectorialic 

acid. On Mt Kenya one thallus was collected of a secondary isidiate morphotype 

with red pigment in the cortex and containing thamnolic and alectorialic acids. It 

seems to be an unusual chemotype of U. rubicunda but is left undetermined for 

the time being. 

Occasional plants have been found which, despite repeated testing, proved to be 

exceptions to the usual chemical groupings. For instance, the presence of protocetraric 

acid in the thallus nearly always excluded the finding of salazinic acid, but 

in a few plants both undoubtedly occurred. Again, though the subcortical red 

pigment was nearly always associated with protocetraric acid, it was found in a few 

plants of U. subflorida with norstictic or salazinic acid and in two collections of U. 

bicolorata with alectorialic acid. 

Species delimitation 

Classification of the material by (1) propagules and (2) pigmentation resulted in the 

arrangement set out in Table 1. This shows that each of the pigmented categories


contains a single species and that each of the non-pigmented categories contains 

several species. A question that needs to be considered, therefore, is whether the 

pigmented species are too broad in concept, that is, whether each should be split 

into several species. Is the presence of pigmentation being used to override other, 

genuine differences ? 

Owing to the morphological variability of all these species a test of homogeneity 

in that respect in the pigmented species could not be devised, but chemical homogeneity 

could be examined. The main chemical races found in the species to which 

all the East African specimens were ultimately assigned are summarized in Table 2. 

The numbers of chemotypes (excluding depsidone-deficient ones) are shown in the 

three non-pigmented groups and the six pigmented groups derived from the 

classification of Table 1. On the whole the results indicate a fair degree of homogeneity 

in each pigmented taxon and certainly a greater homogeneity than in the 

TABLE 1. Classification of corticolous fruticose species by propagula and pigmentation 

Primary species 

Non-pigmented: U. complanata, U. submollis, U. albotnaculata, U. intumescens, U. picta, 

U. nodulosa* 

Pigmented: Pigment restricted to cortex—U. sanguinea*. Pigment mainly subcortical 

in medulla—U. subflorida 

Sorediate species 

Non-pigmented: U. abissinica, U. aristata, U. perplexans, U. ruwenzoriana, U. subeciliata, 

2U16/10t 

Pigmented: Pigment mainly subcortical in medulla—U. bicolorata 

Isidiate species 

Non-pigmented: U. undulata, U. leprosa, U. incrassata, U. perhispidella 

Pigmented: Pigment restricted to cortex—U. rubicunda. Pigment mainly subcortical in 

medulla—U. sorediosula. Pigment mainly periaxial in medulla—U. roseola. 

* Species newly described in this paper. 

t Specimen not assigned to species (see text). 

TABLE 2. Numbers of chemotypes in each group of species 

of corticolous fruticose Usneas 

Species group 

Primary species 

Non-pigmented 

Pigmented (cortex) 

Pigmented (medulla) 

Sorediate species 

Non-pigmented 

Pigmented (medulla) 

Isidiate species 

Non-pigmented 

Pigmented (cortex) 

Pigmented (medulla, subcortical) 

Pigmented (medulla, periaxial) 

Number of 

chemotypes 

8 

1 

3 

5 

2 

5 

2 

1 

1


non-pigmented groups. (The most exceptional case in the pigmented groups, 

namely, the primary species with pigmented medulla (Usnea subflorida), with three 

chemical races, had two of those represented at only three out of the 22 localities 

from which collections of this species were made.) 

The three non-pigmented groups were then examined in order to delimit the 

species within them, and they are discussed in turn below. 

In the group of non-pigmented primary species Usnea picta could be separated 

out as a robust species with stiff branches and many tubercles rather than papillae. 

The stiffness of the branches appears to be due partly to the thickness of the cortex, 

and this character was therefore compared in plants assigned respectively to U. 

picta, U. submollis, and U. nodulosa. (Both the last two species have robust morphotypes 

that might be compared with U. picta, whereas U. complanata is a slenderer 

species and U. albontaculata has other differences, discussed below.) Five specimens 

of U. picta, U. submollis, and U. nodulosa were chosen of comparable size, three 

main branches from each were sectioned, and the width of the cortex was measured 

microscopically to the nearest 0-05 mm. Since both inner and outer surfaces of the 

cortex are ridged and nodular, the width was measured so far as possible at points 

without these irregularities. The results are shown in Table 3. Though the differences 

are slight they are fairly consistent and when tested further were found to be 

taxonomically helpful if interpreted as follows: the cortex of U. picta is usually 

0-1 mm thick or more, while in the other species it is usually less. 

TABLE 3. Mean width of cortex (mm) of three branches from five specimens of species indicated 

Species 

1 

2 

Specimen 

3 

4 

5 

Grand 

mean 

U. picta 

U. submollis 

U. nodulosa 

010 

010 

008 

013 

009 

008 

011 

008 

010 

011 

009 

009 

009 

009 

008 

011 

009 

009 

Like Usnea picta, U. nodulosa has tubercles rather than papillae; they are often 

elongate or effigurate as well as orbicular. However, U. nodulosa has branches that 

are more pliant owing to their thinner cortex, more often develop laterally instead of 

by isotomic dichotomy, and are more often fusiform than tapered. 

The other species in this group are characterized by having papillae and small 

nodular tubercles rather than the larger, linear or effigurate tubercles of Usnea picta 

and U. nodulosa. These species are Usnea complanata, U. submollis, and U. albomaculata. 

(U. intumescens Mot., a doubtful species in the U. submollis aggregate, 

also comes into this group but is excluded from separate consideration: see under 

U. albomaculata below.) It appeared from our material that the frequency of spinules 

varied inversely with that of papillae or tubercles. Some specimens are intermediate 

in this respect, and decisions on them were doubtful. However, after 

examining the types of these three species we assigned our specimens to two main 

groups. The first group, with the frequency of spinules high and of papillae low, 

was taken to represent U. complanata. The second group, with the frequency of 

spinules low and of papillae high, was taken to represent U. submollis and U. 

albomaculata.


Separated on this basis, the two groups remained mixed chemically, but when they 

were examined in relation to the altitude at which they were collected a distinct 

difference was found (Table 4). In making this comparison we included only those 

specimens collected in East Africa and excluded those collected by Stauffer on the 

Virunga Volcanoes, as they were all or nearly all just outside our area. The montane 

zone begins at around 2000-2500 m altitude. Table 4 shows that 34 out of 39 

localities (87%) for the Usnea complanata aggregate were below this altitude, 

whereas for the U. suhmollis aggregate only six out of 49 localities (12%) were 

below it. 

TABLE 4. Numbers of collections at separate localities of U. complanata and U. submollis 

aggregates analysed by chemotype and altitude 

Chemotype 

U. complanata aggr. 

psoromic 

salazinic 

norstictic 

stictic 

U. submollis aggr. 

alectorialic +_ salazinic 

norstictic ± salazinic 

psoromic 

stictic 

fumarprotocetraric 

— — — — 

— — — — 

1 

2 

Altitude (m) 

A 

1000- 

9 

3 

— 

5 

1 

1 

— 

1500- 

10 

3 

3 

1 

4 

— 

— 

2000- 

— 

3 

\ 

— 

6 

1 

1 

2500- 

— 

1 

— 

— 

9 

1 

4 

3000- 

— 

— 

— 

— 

10 

2 

2 

3500 + 

— 

— 

—— 

3 

1 

— 

— 

— 

Further 1 division of the Usnea complanata aggregate was considered but rejected. 

A number of morphotypes were recognizable, however, and details are reported 

under U. complanata in the systematic section below. 

In the Usnea suhmollis aggregate, though several taxa with similar morphology 

and chemistry are reduced to synonymy, U. albomaculata is retained as separate for 

the time being. But whether it is specifically distinct from U. submollis is doubtful. 

Its type differs from the latter species in having some scattered large pseudocyphellae 

on the main branches, extensive efflorescence of medullary tissue from 

cracks and articulations, a black base to the thallus, and psoromic acid. At least 

some of the pseudocyphellae have been formed by a branch or fibril breaking off, 

enlargement of the cortical aperture thus left, and extrusion into it of medullary 

tissue, with the broken end of the axis of the branch or fibril remaining in the centre. 

These cortical openings might therefore more aptly be described as scars than 

pseudocyphellae, though they seem capable of serving the function of gas exchange. 

The extent to which such pseudocyphellae and/or medullary extrusions from 

cracks and joints are developed varies over a continuous range from absence to 

abundance. 

The presence or absence of a black base may be difficult to determine. Even when 

well developed, the blackening does not extend more than about 5 mm above the


base, and it is usually less, often about 1 mm. Doubtful specimens in which it 

extends only partly round the stem or is patchy or covers even less than 1 mm of 

stem are fairly frequent. 

Despite some doubtful specimens, however, which we have excluded, it was found 

possible to classify 51 specimens of the Usnea submollis aggregate from separate 

localities by pigmentation of the base, presence or absence of large pseudocyphellae, 

and chemistry. (The sample included eight specimens from Ethiopia deposited by 

Italian collectors in FI.) The results are given in Table 5. They show that most of 

the specimens with alectorialic and/or salazinic acid lacked large pseudocyphellae 

and had a pale base, while most of those with other chemistry had large pseudocyphellae 

and a black base, but there is some overlap. In the alectorialic/salazinic acid 

group 11 out of 28 (39%) had the 'wrong' characters of large pseudocyphellae or 

black base or both, and in the group with the other chemistry six out of 23 (26%) 

had the 'wrong' characters of no large pseudocyphellae or pale base or both. To 

these specimens of doubtful status because of'wrong' characters must be added the 

specimens, about another 10%, excluded from the analysis because the classifying 

characters of large pseudocyphellae or black base or both could not be precisely 

determined. 

TABLE 5. Classification of 51 specimens of the U. submollis-albomaculata 

aggregate by large pseudocyphellae, colour of thalline base, and 

chemistry 

Chemistry 

Large PSC* absent Large PSC* present 

Pale base Black base Pale base Black base 

alectorialic + salazinic 

psoromic 

norstictic 

stictic 


17 

0 

0 

0 

0 

7 

2 

1 

1 

0 

2 

0 

1 

0 

1 

2 

8 

7 

1 

1 

* PSC=pseudocyphellae. 

The delimitation of Usnea albomaculata from U. submollis is therefore made on 

somewhat unreliable criteria. But because a majority of plants can be separated 

into one or other group by those criteria we retain the two species for the time being. 

The five species in the Usnea abissinica group were found to be morphologically 

indistinguishable. The thallus in all was often rather small (about 5 cm long) with 

slender and flaccid branches, though the main branches were sometimes disproportionately 

thick. The commonest species of this group, U. perplexans, was the 

only one recorded below 2500 m, and most of its localities were higher (Table 6). 

The differentiation of these sorediate species was made on chemical criteria. The 

chemical substances found are set out in Table 7. This classification can only be 

regarded as provisional, because the number of specimens was small and there is 

room for debate as to how the chemistry should be interpreted in several cases. 

For instance, we have seen only one collection of Usnea abissinica, and it is based on 

specimens producing norstictic acid as the primary substance. But norstictic acid


was present in small amounts, regarded as accessory, in a specimen assigned to U. 

subeciliata owing to its containing fatty acids. Again, while specimens containing 

fatty acids with or without salazinic acid were assigned to U. subeciliata, two 

containing fatty acids plus salazinic acid were considered probably to belong under 

U.perplexans because they also contained the 'pink unknown' substance. However, 

it is possible they should be assigned to U. subeciliata. 

TABLE 6. Numbers of localities at altitudes shewn where indicated species were collected {disparities 

between this Table and those for the chemistry of the species are due to differences in the information 

available for some specimens) 

Altitude (m) 

Species 

1000- 

1500- 

20CO- 

25C0- 

3000- 

3500- 

4000 + 

abissinica 

ruwenzoriana 

aristata 

subeciliata 

perplexans 

albomaculata 

bicolorata 

subflorida 

submollis 

sorediosula 

leprosa 

undulata 

rubicunda 

sanguinea 

perhispidella 

picta 

complanata 

incrassata 

nodulosa 

roseola 

— 

— 

— 

— 

— 

— 

— 

— 

2 

2 

2 

4 

3 

— 

1 

— 

17 

10 

10 

1 

— 

— 

— 

— 

2 

1 

2 

1 

4 

2 

4 

17 

14 

2 

8 

7 

17 

3 

1 

1 

— 

— 

— 

— 

4 

1 

2 

3 

7 

4 

3 

17 

8 

— 

3 

— 

4 

— 

— 

— 

— 

— 

1 

1 

5 

3 

4 

9 

1 

1 

2 

— 

1 

— 

— 

1 

— 

— 

— 

1* 

2 

3 

3 

4 

6 

9 

9 

10 

— 

— 

1 

— 

— 

— 

1 

— 

— 

— 

— 

1 

1 

4 

2 

— 

2 

2 

4 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

1 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

* Estimated from description of species. 

Usnea intumescens is omitted as it is not certainly known from our area. 

Detailed information on blackening of the base of the thallus in this group is 

recorded under each species below. As noted above, it was an unreliable discriminating 

character. 

The four isidiate non-pigmented species in the Usnea undulata aggregate have 

been discussed previously (Swinscow and Krog, 1975). The limits of each were 

found to be indistinct both morphologically and chemically, and their circumscription 

depended to a great extent on probabilities, as in the U. complanata and 

U. submollis aggregates. 

Ecology and distribution 

While additional details are recorded below under the individual species, some 

general comments are made here. Below 2000-2500 m altitude, which approxi-


mately limits the montane zone, the fruticose Usneas were found mainly on the 

small branches and twigs of shrubs, while at higher altitudes they were also common 

on the large branches of forest trees. The altitudes of the collecting localities were 

known for 289 specimens, and they are set out in Table 6. The species from and 

including U. sorediosula downwards in the Table had 95% of their localities below 

the montane zone, whereas the species from and including U. submollis upwards 

had 75% of their localities in the montane zone. The montane species were frequently 

bathed in mist, cloud, or rain. Those at lower altitudes were mainly on 

mist-affected hills and plateaux at about 1000-2000 m. Below that level Usneas 

were rare, even at the coast. 

The two commonest species below the montane zone were Usnea complanata and 

TABLE 7. Numbers of localities for chemotypes of each species in the 

sorediate non-pigmented group 

Species and 

Chemotypes 

U. abissinica 

Type: 

Other: 

U. aristata 

Type: 

Other: 

norstictic 

fumarprotocetraric -f- barbatic (trace) 


fumarprotocetraric + protocetraric (trace) 

U. perplexam 

Type: salazinic 

U. pulverulenta type: p.p. salazinic; p.p. barbatic 

Other: salazinic 

2 

salazinic + barbatic 

8 

salazinic + constictic +' pink unknown' 3 

salazinic -f fatty acid —'pink unknown' 2* 

U. ruwenzoriana 

Type: alectorialic 

U. ruwenzoriana var. nigroapiculata type: usnic only 

U. irregularis type: protocetraric — alectorialic + salazinic 

Other: protocetraric + alectorialic -f barbatic 

3 

protocetraric+alectorialic — salazinic — 

barbatic 

4 

protocetraric + alectorialic + fumarprotocetraric 

-f barbatic 

1 

alectorialic + squamatic 

1 

alectorialic + Pbarbatic 

1 

U. subeciliata 

Type: fatty acids -f salazinic (trace) 

Other: fatty acids — salazinict 

fatty acids 


j 

localities 1 

* These two specimens could equally well be placed under U. subeciliata. 

t One with norstictic acid also. 

0 

5 

2 

7 

8


U. undulata. These are the characteristic species of twigs and small branches of 

shrubs. U. complanata was the more frequent in towns, being common in gardens, 

parks, and street avenues. 

Most of the species discussed in this paper are widespread in tropical Africa, and 

Usnea rubicunda has a wide distribution in the world's tropical and temperate 

regions. The type of U. roseola is from Japan, and the species is also known from 

Tristan da Cunha. The specimens from those two localities and from Africa are 

unusually homogeneous for this genus. The type of U. perplexans is from the 

Himalayas. Specimens of U. undulata and U. subflorida have been seen from South 

Africa. In the absence of a thorough study of material from other parts of Africa it is 

impossible to say at present whether any of the species recorded here are actually 

restricted to East Africa, or indeed the African continent. 

Discussion 

In the moister parts of the tropics the genus Usnea produces an abundance of 

morpho- and chemotypes. Such is the wealth of variation that the delimitation of 

species having some pretence to biological reality is a considerable problem. Some 

guidelines that we adopted for the pendulous Usneas have been described (Swinscow 

and Krog, 1978). Here we discuss our classification of the fruticose species. 

The value of pigmentation as a character at species level is shown in Tables 1 and 

2. The next step, delimitation of the non-pigmented species by morphological 

criteria, led in the primary and the isidiate non-pigmented groups to aggregates 

rather than clearly recognizable species, as indicated above, while the sorediate 

non-pigmented group proved impossible to divide morphologically. Finally, 

therefore, the species and species aggregates reached by pigmentary and morphological 

classification were analysed in relation to the chemical substances they 

produced. 

The sorediate non-pigmented species are provisionally defined by their chemistry 

alone. And, as indicated above, chemical criteria entered into the delimitation of 

some species in other groups. But the retention of three or four or even more 

chemotypes within a species, even the ill defined species termed aggregates, needs 

some explanation, for to some lichenologists each chemical type denotes a separate 

species, for example, Asahina (1965). There are three main reasons for it. Firstly, 

morphctypes are sometimes represented in small areas by plants showing very 

little variation but of several different chemical races. An interesting example of this 

was found at a locality in Uganda, West Mengo District, Busiro County, altitude 

1100 m. On the upper branches of a fallen tree, thalli of Usnea complanata were 

collected which were found to belong to three chemotypes, namely, psoromic acid, 

salazinic acid, and stictic acid. They had barely discernible morphological differences 

and were all well within the range of variation of a single morphotype of this 

species. Elsewhere even single twigs have been found bearing thalli of the same 

morphology but containing different depsidones. It is hard to believe that such 

differences should be regarded as denoting distinct species. What is worth some 

consideration is whether the haploid spores in an ascus are genetically uniform. It 

seems theoretically possible that spores from a single ascus may give rise to thalli 

producing different depsidones.


Secondly, when a substantial sample of thalli of the same species aggregate is 

examined chemically, the chemistry is rarely correlated satisfactorily with the 

morphological variation. The common finding is of a range of morphotypes each 

including mere than one chemical race. This is specially evident in the U. complanata 

aggregate. 

Thirdly, when a correlation does exist between morphology and chemistry, the 

morphological variation and/or chemical departure from the norm (in the sense of 

average) may be too slight, even though distinct, to be acceptable as a species 

difference. An example of this was provided by some populations of Usneapicta in 

Kenya. On Kilima Kiu 70 km SE of Nairobi two chemotypes were collected. A 

salazinic acid one had more or less terete branches (though bearing many tubercles), 

while a protccetraric acid one had somewhat scrobiculate, ridged branches. At 

Lukenia, 30 km SE of Nairobi, only the protocetraric acid type was collected. The 

plants were slightly scrobiculate and ridged but much less so than those of the same 

chemistry on Kilima Kiu. All these morphological differences are slight and seem to 

represent local morphotypes well below species level. They would be readily 

dismissed as such if the plants had been uniform chemically, but the moderate 

degree of chemical and morphological correlation raises a doubt about their 

taxonomic status. 

Another striking example of this type of correlation was seen in the Usnea 

complanata aggregate. At Lukenia a population of plants is characterized by an 

abundance of spinules giving a bristly appearance, a grey bloom on the cortex, and 

stictic acid. A few similar plants with the same chemistry were found 150 km to the 

south-east. 

We consider that these correlated morphotypes and chemotypes come within a 

single species owing to the small degree by which they differ from the main body \ 

of individuals in the species. Other workers might regard them as forms, varieties, . 

or even species. The question at issue is not their distinctness but at what taxonomic i 

level this should be recognized, if at all. Here we bear in mind that the biology of j 

these plants, so far as it is at present understood, provides no theoretical necessity ! 

for the creation of a taxonomic category for every small departure from the norm j 

(or mean), even though that departure is mainly genetically determined and is j 

correlated with another departure from the norm. Sexually reproducing species j 

would be expected to show some variation, both morphological and chemical, in the " 

individuals composing them. Moreover, by extension of this principle the vegetatively 

reproducing species derived from them would also be expected to show not 

merely environmental but some genetic variation. The nature of that variation 

merits brief discussion. 

In Usnea and perhaps in other genera it seems unlikely that secondary, vegetatively 

reproducing species are generated only once by a primary species. On the 

contrary, it is more probable that individuals of a primary species from time to time 

originate, by mutation, individuals that become the founder members of a secondary 

species. The originating individuals in the primary species may differ genetically, 

and hence morphologically and chemically, between each other though within the ' 

limits of a single species. Their secondary progeny will reflect those differences. 

Hence populations of isidiate and sorediate plants may grow up that are derived • 

from the same species yet have distinct and perpetuating differences. In so far as ; 

such populations, reproducing vegetatively, can be supposed to have originated !


from a single primary species we regard them as constituting a single secondary 

species, provided they have remained morphologically and chemically close to one 

another. But it is of course possible that a population of that kind may evolve by 

one of the recognized methods of speciation into separate species. In this connexion 

it is worth noting that apothecia are not uncommon in secondary species, so that 

genetic exchange in sexual reproduction cannot be ruled out. 

In view of this our treatment of the sorediate non-pigmented group needs 

further explanation, since we have retained five species defined on chemical criteria 

in the absence of consistent morphological differences. The material consists of 

relatively few specimens from localities scattered over a wide geographical area at 

high altitudes (mostly around 3000 m). The one or more primary species from which 

several of these sorediate counterparts have evolved are not clear. Owing to the 

restriction of the species in this group except Usnea perplexans to high altitudes it is 

possible that the primary species from which they have evolved have their main 

prevalence in the temperate regions, as do a number of species in other genera whose 

only localities in East Africa are high in the mountains. Furthermore it is possible 

that sorediate plants of indistinguishable morphology are ultimately the descendants 

of different primary species, and this may or may not be reflected in their differing 

chemistry. Consequently we think it would be premature to reduce these taxa to 

synonymy. 

Some of the isidiate and sorediate species found in East Africa appear to be 

derived from the primary species in the same area. A clear example of this is the 

chemotype of Usnea rubicunda containing salazinic and norstictic acids. Its primary 

counterpart is the newly described U. sanguinea, which has the same chemistry and 

type of pigmentation. Again, the primary species of U. subflorida, with subcortical 

pigment and protocetraric acid as its main chemical substance, may have for its 

isidiate counterpart the very similar U.sorediosula and for its sorediate counterpart 

U. bicolorata. All three have the same type of medullary pigmentation together 

with protocetraric acid. However, certain differences are also noteworthy. The 

thalline base is pale in U. sorediosula but black in the other two species. And while 

U. subflorida and U. bicolorata are plants of high montane forest, U. sorediosula 

prefers woodland below 2500 m. But one plant has been collected (K 341103a) 

from 2800 m on Mt Kenya in montane forest that does appear to be a complete 

isidiate counterpart of U. subflorida, with a black base, pigment in the cortex and 

here and there in the medulla, and protocetraric acid. 

The complex of morphotypes in the Usnea complanata and U. submollis aggregates 

seem to have isidiate counterparts in the U. undulata-leprosa-perhispidella aggregate. 

Chemotypes with salazinic acid are common in both, while the race galbinic plus 

norstictic plus trace of salazinic acid, so characteristic of U. undulata, has been 

found in three collections assigned to U. complanata. Moreover, U. incrassata, 

whose two main chemical races are salazinic and protocetraric acids, would seem 

to have its primary counterpart in U.picta, with the same chemical strains. 

Finally, one specimen (2U 16/10) appears both morphologically and chemically 

to be a possible isidiate counterpart of the newly described Usnea nodulosa. Both 

primary and secondary species contain constictic acid and the 'pink unknown' 

and the effigurate tubercles of U. nodulosa have their parallel in 2U 16/10, 

which has many secondary soralia that seem to have developed on similar 

tubercles.


Key to the fruticose species of Usnea subgenus Usnea in East Africa 

1. Thallus corticolous (or, rarely, on earth and among plant roots on rocks).... 2 

Thallus saxicolous, firmly attached to rock in high moorland and alpine 

zones 18 

2(1). Isidia sparse or absent; soralia absent; apothecia usually numerous 3 

Isidia or soralia or both numerous;apothecia few or absent 9 

3(2). Thallus pigmented (pigment may be obscure in medulla) 4 

Thallus non-pigmented 5 

4(3). Pigment restricted to cortex 18. U. sanguinea (p. 243) 

Pigment mainly subcortical in medulla but also in cortex 

21. U. subflorida (p. 246) 

5(3). Papillae and tubercles absent or sparse; spinules numerous 

6. U. complanata (p. 229) 

Papillae and/or tubercles numerous; spinules sparse 6 

6(5). Tubercles mainly effigurate,linear, or verrucose; papillae few 7 

Tubercles mainly conical or hemispherical; papillae numerous 8 

7(6). Branches somewhat angulate and stiff; tubercles large (c. 0-3 mm diam) 

13. U. picta (p. 236) 

Branches terete, more pliant; tubercles smaller (c. 0-1-0-3 mm diam) 

10. U. nodulosa (p. 232) 

8(6). A few large pseudocyphellae on main branches, with extrusion of medullary 

tissue from cracks and joints 2. U. albomaculata (p. 221) 

Large pseudocyphellae lacking, and medullary extrusion absent or sparse 

22. U. submollis (p. 247) 

9(2). Pigment periaxial in medulla, pink ('strawberry ice cream'); both isidia 

and true soralia numerous 15. U. roseola (p. 238) 

Pigment absent or, if present, not periaxial but subcortical or cortical and 

red to ochraceous; either isidia or true soralia numerous 10 

10(9). Isidia numerous; pseudocyphellae numerous; soralia if present secondary 

on pseudocyphellae 11 

Primary excavate (or later efflorescent) soralia numerous; isidia absent; 

pseudocyphellae absent or sparse 16 

11(10). Thallus pigmented 12 


12(11). Pigment restricted to cortex 16. U. rubicunda (p. 240) 

Pigment mainly subcortical in medulla but also in cortex 

19. U. sorediosula (p. 245) 

13(11). Isidia densely clothing branches along their length ('pipe cleaner' appearance) 

11. U. perhispidella (p. 235) 

Isidia mainly in clumps on pseudocyphellae 14


14(13). Branches somewhat angulate or scrobiculate, with pseudocyphellae on 

ridges 7. U. incrassata (p. 232) 

Branches terete 15 

15(14). Some branches inflated-fusiform; some pseudocyphellae elongate 

8. U. leprosa (p. 232) 

Branches normally tapered; pseudocyphellae punctiform to orbicular.. .. 

23. U. undulata (p. 250) 

16(10). Thallus pigmented 4. U. bicolorata (p. 227) 


17(16). Thallus up to c. 4 cm high, with slender, pliant branches (plants mostly of 

high altitudes, c. 3000 m) 1. U. abissinica aggr. (p. 221) 

(For chemical differentiation of 1. U. abissinica, 3. U. aristata, 12. U. 

perplexans, 17. U. ruwenzoriana, and 20. U. subeciliata see Table 7, 

p. 216.) 

Thallus over 4 cm high, with more robust branches (plant of lower altitude, 

under 2000 m) Specimen 2U16/10 (see under U.nodulosa (p. 232) 

18(1). Thallus pigmented red, with considerable blackening at base 

9. U. maculata (p. 232) 

Thallus lacking red pigment, with or without blackening at base 19 

19(18). Thallus robust, mostly 5 cm or more high; pseudocyphellae, often large, 

on main branches; base usually blackened.. 5. U. bornmuelleri (p. 229) 

Thallus more delicate, mostly less than 5 cm high; pseudocyphellae absent 

from main branches; base usually concolorous 14. U. pulvinata (p. 236) 

1. Usnea abissinica Mot. (Fig. 1) 

The Species 

Lich. Gen. Usnea Stud. Monogr., Pars Syst. 3: 621 (1938); type:—Schimperi iter abyssinicum, 

s ect. 2, no. 436, Abyssinia in regione boreali media montis Silke, ad truncos Ericae acrophyae, 

20 February 1840, Schimper (UPS-holotype!; S-isotype!). Chemistry: Usnic and norstictic 

acids. 

Thallus fruticose, non-pigmented, with base slightly blackened. Branches 

tapered, terete, slender, pliant. Spinules sparse. Papillae numerous, dense. Tubercles 

scattered. Pseudocyphellae mainly on tubercles but a few punctiform plane on 

cortex. Isidia sparse. Primary soralia numerous, excavate to plane or protuberant. 

Apothecia present. 

This species is known only from Schimper's exsiccata. Nearly all the thalli are 

fruiting freely. It is distinguished from other members of the sorediate group by its 

main chemical substance being norstictic acid. 

For chemistry of the sorediate non-pigmented species see Table 7 (p. 216). 

2. Usnea albomaculata Mot. (Figs 2-3) 

Lich. Gen. Usnea Stud. Monogr., Pars Syst. 3: 620 (1938); type:—Abissinien, Isaak Debre,


I 

FIG. 1. Usnea abissinica (holotype). Fibrils bear small soralia. Rule=l cm.


1862, Stendrner (S-isotype!; B-holotype, presumed lost). Chemistry: Usnic acid, psoromic 

acid, conpsoromic acid. 

Usnea blepharoides Dodge, Ann. Mo. hot. Gdn 43: 395 (1956); type:—Kilimandjaro, obern 

Waldrand, alt. 3000 m, 8 December 1932, Geilinger 4417 (BM—holotype!). Chemistry: 

Usnic, psoromic and conpsoromic acids. 

Thallus fruticose, non-pigmented, with black base. Branches often somewhat 

fusiform, terete, with articulations and broken off bases white owing to protrusions 

of medullary tissue. Spirrules sparse. Papillae numerous, dense. Tubercles few to 

numerous. Pseudocyphellae on tubercles, and generally also some large pseudocyphellae 

on the plane cortex of the main branches. Isidia absent to sparse. Soralia 

absent. Apothecia usually present. For chemotypes see Table 8. 

TABLE 8. Numbers of localities for chemotypes of Usnea albomaculata 

Chemotype 


localities 

psoromic 

norstictic : salazinic 


Within the Usnea submollis aggregate this species is differentiated by a combination 

of the black thalline base, large pseudocyphellae on the main branches with efflores- 

FIG. 2. Usnea albomaculata (T 12.7). Somewhat swollen main branches and few spinules, as in 

U. submollis also (Fig. 19). Rule 1 cm.


FIG. 3. Usnea albomaculata (right), containing norstictic acid, and U. submollis (left), containing 

salazinic acid, with mingled holdfasts. Upper arrow points to pseudocyphella, lower arrow 

to black base. Rule = 1 mm.

1979 Usnea in East Africa— Swinscow & Krog 225 

cence of medullary tissue from the cracks and articulations, and its chemistry. But, 

as reported above (p. 214), a study of these characters showed them to be of only 

partial value in differentiating the species. 

Forest trees and ericaceous shrubs at about 3000-4000 m have the twigs often 

covered with small thalli 2-4 cm high of the Usnea submollis aggregate and U. 

subflorida. The isotype of U. simplicissima Mot. (BM!) consists of such thalli; it was 

collected on 'Ruwenzori, etage alpin 4000 m, abondant sur Hypericum, juillet 1932, 

Hauman 952.' The specimen contains usnic, fumarprotocetraric and protocetraric 

acids. Owing to the small size of the thalli and their lack of distinctive characters it 

is impossible to be certain of the species they belong to, but their chemistry suggests 

they might appropriately be placed under U. albomaculata. Similar material from 

Kilimanjaro, but containing salazinic acid, has been issued as U. simplicissima in 

Vezda's, Lich. sel. exs. no. 1174 (BM!); it probably belongs to U. submollis. 

The type of Usnea intumescens Mot. was collected by Stauffer in either Rwanda 

or Uganda on ' Mgahinga Osthang 3350 m/M, Uebergang Senecietum-Hypericum- 

Busch, Epiphyten an Hypericum u. Rhod.blattbaum,' on 15 November 1954 

(BERN 3260/797!). It contains usnic, fumarprotocetraric and protocetraric (trace) 

acids. The thalline base is pale. This species belongs to the U. submollis aggregate. 

Its chemistry and extruded medullary tissue suggest it should be assigned to U. 

albomaculata, while its pale base is more concordant with U. submollis. Motyka also 

determined as U. intumescens a number of other specimens collected by Stauffer 

(BERN!) in the same area and further south. Some contain norstictic, others 

psoromic acid; at least one contains salazinic and alectorialic acids, a combination 

characteristic of U. submollis; and one contains fumarprotocetraric acid, like the 

type (we did not test all specimens). Since most of this material, and perhaps all of it, 

came from outside our area we have not included it in our attempts to delimit 

separate species in the U. submollis aggregate. Much of it, however, belongs to U. 

albomaculata on the criteria by which that species is delimited here, admittedly 

somewhat questionably, from U. submollis. 

Usnea albomaculata grows in the montane forest and ericaceous zone, often 

mixed with U. submollis. 

East African specimens examined: Ethiopia: Shewa Province, Menegesha, Tapper 533c 

(BM). Arussi Province, E of Asella, E 31/36.—Kenya: Rift Valley Province, ElgeyoMarakwet 

District, Cherangani Hills 10 km S of Labot, 2K 8131; Trans Nzoia District, Mt Elgon, 

Ryvarden 9372 (O). Eastern Province, Mem District, Mt Kenya, N slope, 4K 20/110, 111, 

4K 24/103, 106.—Tanzania: Northern Province, Arusha District, Mr Mem W side, 

T 12/7.—Uganda: Karamoja District, Matheniko County, Mt Moroto near Sogolomon, 

2U 36/61-lb, Wilson (BM). Bugisu District, North Bugisu County, Mt Elgon near Sasa Hut, 

2U 44/15, 25, 57, 91. Kigezi District, Bufumbira County, Muhavura N side, U 16/20-2. 

3. Usnea aristata Mot. (Fig. 4) 

Persoonia 1: 430 (1961); type: Kenya, Nyanza Province, Kisumu-Londiani District, Tinderet 

Forest Reserve, Camp 2, 0°6'30"S, 35°29'E, on low trees and shrubs, mainly Tarchonanthus 

sp., edge of forest, exposed, 2420 m alt, 20 June 1949, Maas Geesteranus 11050 p.p. (L— 

lectotype designated here). Chemistry: Usnic acid, fumarprotocetraric acid, barbatic acid 

(trace). 

Thallus as in Usnea abissinica except that the base is pale in the type and a few 

other specimens, but in most black. Apothecia rare (one seen, lacking formed

FIG. 4. Usnea aristata (K 26/46). Slender branches and numerous small soralia. Rule—1 cm.


hymenium). Fumarprotocetraric acid is found in all specimens, with or without 

protocetraric and barbatic acids as accessory substances (see Table 7). 

This is a species of upper montane forest and the ericaceous zone at around 

3000 m altitude, and it grows mainly on the smaller branches of sheltered shrubs. 

East African specimens examined: Ethiopia: Bale Province, below Likumsa, Tapper 718b 

(BM); 2 km ENE of Little Batu, Tapper 994c, 997 (BM).—Kenya: Central Province, 

Nyeri District, Aberdare Mountains E of Lesatima, K 26/46,508,5K 9\28,529,5K13/21,23b. 

4. Usnea bicolorata Mot. (Fig. 5) 

Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2: 336 (1937): type: not traced. 

Usnea dichroa var. virgulata Mot., Annls Univ. Mariae Curie—Skhdowska, C, 11: 120 (1959) 

['1956']; type: Niragongo, Shaherukrater (2700 m/M) und bis 2800m, Cornaceen-Uebergangswald 

mit Hypericum, 11 September 1954, Stauffer 3153/340 p.mp. (BERN—holotype!). 

Chemistry: Usnic, protocetraric, alectorialic, and salazinic acids, pigment. 

Usnea griseola Mot., Annls Univ. Mariae Curie-Skhdowska, C, 11: 120 (1959) ['1956']; 

type: Nkanda, 2700 m/M, im Hang gegen dem Sattel, an Hypericum und Ericaceen, 26 

November 1954, Stauffer 33 98/ 984 (BERN—holotype!). Chemistry: Usnic acid, protocetraric 

acid, alectorialic acid, salazinic acid, pigment. 

Usnea bicolorata var. pseudorubescens Mot., Annls Univ. Mariae Curie—Skhdowska, C, 11: 

122 (1959) ['1956']; type: Muhavura 3300 m/M, auf schrag aufsteigendem Stamm eines 

Rhodblattbaumes 862, Oberseite, 19 November 1954, Stauffer 3370/872 (BERN—holotype!). 

Chemistry: Usnic, protocetraric, alectorialic, and barbatic acids, pigment. 

Thallus fruticose,with red to ochraceous pigment subcortical in medulla and also 

in cortex, occasionally only in cortex; base black. Branches tapered, terete, slender, 

pliant. Spinules sparse. Papillae numerous. Tubercles few. Pseudocyphellae none 

to very sparse. Isidia absent to sparse. Soralia numerous, mainly excavate to plane 

or protuberant. Apothecia rare. Spores 10-13 X 7-9 urn. For chemical races see 

Table 9. 

In the absence of the type specimen we have relied for the identification of this 

species on the type of Usnea bicolorata var. pseudorubescens and a comparison of 

Motyka's descriptions of U. bicolorata and its var. pseudorubescens. He refers 

unambiguously to the patchy red pigmentation and the soralia. 

The distinguishing features are the slender branches (though a few of the main 

branches may be disproportionately thick); true soralia, especially on the distal 

branches; and the pigment, which is usually subcortical. The alectorialic acid in the 

soralia gives Pd+yellcw as distinct from the Pd+orange reaction of the protocetraric 

acid in the medulla. 

This species is found mainly on shrubs in the upper parts of the montane forest 

and in the ericaceous zone around 3000 m altitude. 

TABLE 9. Numbers of localities for chemotypes of Usnea bicolorata 

Chemotype 


localities 

protocetraric ± alectorialic* i salazinic ± barbatic 20 

alectorialic* f barbatic 2 

* In soralia only

FIG. 5. [/.t«ea bicolorata (K 26/8a). Slender branches and numerous small soralia. Rule==l cm.

1979 Usnea in East Mricz—Swinscow & Krog 229 

East African specimens examined: Ethiopia: Bale Province, Dinshu Hill, Tapper 944 (BM); 

1 km E of Dinshu, Tapper 913 (BM).—Kenya: Rift Valley Province, Elgeyo Marakwet 

District, Cherangani Hills 20 km S of Labot, 2K 7)523; Trans Nzoia District, Mt Elgon, 

Ketner-Oostra 1906b. Central Province, Nyeri District, Aberdare Mountains E of Lesatima, 

K 26/8, 32-2a, 500; Mt Kenya W side near Naro Moru track, K 31136a, K 3313c, 3d, 5b 

K 34jl, 2K 35)28, 2K 36)43, 163. Central Province, Kirinyaga District, Mt Kenya near 

Castle Forest Station, K 49)19b, 19c, K 51 )34b —Tanzania: Northern Province, Arusha 

District, Mt Meru crater, T 5)27; Mt Meru W side, T 13)18. 

5. Usnea bornmuelleri Steiner 

See Swinscow and Krog (1976a: 25, figs 1-2). 

The following species are here reduced to synonymy with Usnea bornmuelleri: 

Usnea cacumir.um Mot., Annls Univ. Mariae Curie-Sklodowska, C, 11: 142(1959) ['1956']; 

type: Muhavura 3950 m/M, Stauffer 3247)762 (BERN—holotype!). Chemistry: Usnic, 

psoromic, and conpsoromic acids. 

Usnea magnified Mot., Annls Univ. Mariae Curie-Sklodowska, C, 11: 143 (1959) ['1956']; 

type: Muhavura, Gipfelregion 4000 m/M, Felsabbruch in Bachrunse, N-expos., 10 November 

1954 Stauffer 3235)760 (BERN—holotype!). Chemistry: Usnic, psoromic, and conpsoromic 

acids. 

Usnea anormalis Mot., Annls Univ. Mariae Curie-Sklodowska, C, 11: 145 (1959) ['1956']; 

type: Muhavura Gipfel, 4120 m s.m., 10 November 1954, Stauffer 3233)758 (BERN—holotype!). 

Chemistry: Usnic and norstictic acids. 

One corticolous specimen of this normally saxicolous species has been seen 

(Uganda, Toro District, Kilembe Mine path to Watamagubu, on stems of Helichrysum 

stuhlmannii, alt 11 850 ft, 19 August 1971, Pentecost RE 55, BM). 

6. Usnea complanata (Mull. Arg.) Mot. (Figs. 6-7) 

Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 109 (1936).—Usnea barbata var. strigosa f. 

complanata Mull. Arg., Hedtvigia 31: 276 (1892); type: In truncis Bachit 7500', Abyssinia, 

1851, Schimper 14 (G—holotype!). Chemistry: Usnic, psoromic, and conpsoromic acids. 

Usnea obtusata Mot., Lich. Gen. Usnea Monogr., Pars Syst. 3: 622 (1938); type: Schimperi 

iter abyssinicum No. 416, Ad arborum corticem in latere boreali montis Kubbi, 26 Juni 1837 

(W—holotype!). Chemistry: Usnic acid. 

Thallus fruticose, non-pigmented, with pale base. Branches tapered, terete or 

slightly angulate. Spinules numerous and sometimes dense. Papillae and tubercles 

few to none. Pseudocyphellae few to none. Isidia absent to sparse. Soralia absent. 

Apothecia always present. Spores 9-11 X 6-8 urn. For chemical races see Table 10. 

The two main chemotypes of this species, psoromic acid and salazinic acid, show 

no consistent morphological differences. Norstictic acid is sometimes an accessory 

substance present in small amounts, and sometimes the main depsidone produced. 

Specimens containing it do not differ appreciably from those of the two main races. 

Two collections from different parts of western Kenya {4K 7/101 and Burnet L 23) 

have been found to contain the 'pink unknown' in addition to salazinic acid. 

A distinct morphotype containing stictic and constictic (± norstictic) acids has 

been collected south-east of Nairobi at Lukenia and near Kibwezi. It is intensely 

spinulose, entirely lacks papillae and tubercles, generally has a 'bloom' on the 

cortex, and also has a rather thick cortex (over 01 mm), so that it is stiff and bristly.

complanata (U 1/3). Relatively small thallus (compare U. submollis in Fig. 19) and spinulose branches. 

Rule—1 cm.


Another series of specimens containing stictic and constictic acids was collected 

in southern Uganda from the Kampala region south-westwards (U 9/23, 3U 9/13a, 

Lye 211, 3U 31/7, 3U 32/8). The first three collections are entirely concordant with 

the usual forms of Usnea complanata; the latter two are more papillose and approach 

U. submollis. One of these collections is referred to above (p. 217). It was made from 

the fallen branches of a tree by a track 16 km south-west of Kampala. From that 

heap of branches morphologically indistinguishable thalli were collected with (1) 

stictic acid, (2) psoromic acid, and (3) salazinic acid as the main depsidones. 

FIG. 7. Usnea complanata (U 1/3). Many spinules, few papillae or tubercles. Rule=l mm. 

TABLE 10. Numbers of localities for chemotypes of Usnea complanata 

Chemotype 


localities 

psoromic conpsoromic 

salazinic —' pink unknown' 

salazinic + trace unknown 

total salazinic (main substance) 

norstictic — salazinic (accessory) 

galbinic + norstictic — salazinic/connorstictic 

stictic — constictic ^norstictic (trace)* 

stictic — constictic — norstictict 

fatty acid 

usnic acid only 

* Morphotype with dense spinules. 

t Morphotype with sparser spinules. 

3 

9 

20 

12 

5 

3 

2 

5 

1 

1


Three collections have been made of a chemical race containing galbinic, norstictic, 

and salazinic acids. They were, respectively,from Ethiopia (s.n.,O), Tanzania 

(/. N. Bjornstad 849e), and Uganda (2U 9/73). Their chemistry and appearance 

suggest that they represent the primary species of that common chemical race in 

the isidiate species Usnea undulata. 

Usnea complanata is widespread at around 1000-1800 m altitude in East Africa, 

often in man-made habitats such as parks, street avenues, and plantations. It is the 

commonest species of Usnea in such places. Localities are too numerous to list 

individually. 

7. Usnea incrassata (Mull. Arg.) Mot. 

See Swinscow and Krog (1975: 132, plate 4A-B). 

8. Usnea leprosa Mot. 

See Swinscow and Krog (1975: 126, plate 3B). 

9. Usnea maculata Stirt. 

See Swinscow and Krog (1976a: 27, fig. 3). 

The following species are here reduced to synonymy with Usnea maculata: 

Usnea rutilans Mot., Annls Univ. Mariae Curie-Sklodowska, C, 11: 123 (1959) ['1956']; 

type: Muhavura 4000 m/M, N, Bachrunse auf Felsabbruch Massenvegetation, 10 November 

1954, Stauffer 3236J760 (BERN—holotype!). Chemistry: Usnic, protocetraric, alectorialic 

acids. 

Usnea vulcanorum Mot., Annls Univ. Mariae Curie-Sklodozvska, C, 11: 141 (1959) [' 1956']; 

type: Kahuzi-Vulkan am Kivusee, Gipfelzone N-expon. Felsplatten, c. 3100 m, 25 January 

1955, Stauffer 3514/1160 (BERN—holotype!). Chemistry: Usnic, protocetraric, and fumarprotocetraric 

aggregate acids. 

The type of Usnea rutilans is exceptionally robust and deeply pigmented. The 

largest thalli are about 15 cm long. A review of the few non-pigmented specimens 

containing protocetraric acid and placed under Usnea bornmuelleri in our paper on 

this aggregate (Swinscow and Krog, 1976a) has shown that they should be assigned 

to U. maculata. Morphologically they are concordant with this species. Depsidonedeficient 

specimens of U. maculata are also now known. 

10. Usnea nodulosa Swinscow and Krog sp. nov. (Figs 8-9) 

Thallus fruticosus, pigmento destitutus. Rami gradatim contracti vel fusiformes, teretes. 

Spinulae sparsae. Papillae sparsae vel nullae. Tubercula numerosa, orbiculares vel lineares 

vel effigurata, verrucascentes. Pseudocyphellae plerumque paucae, ad apices tuberculorum. 

Apothecia plerumque adsunt. Acidum usnicum et acidum consticticum et substantiam 

erubescentem acido sulphurico continens. 

Typus: Uganda, Masaka District, Bukoto County, Jubiya Forest, 0 13'S, 3158'E, alt 

HCOm, on twigs of exposed shrubs, 1971 Swinscow 3U 32J5 (BM—holotypus; O—isotypus). 

Thallus fruticose, non-pigmented, with pale base. Branches often somewhat 

fusiform, sometimes tapered, terete. Spinules sparse. Papillae sparse to none.

FIG. 8. Usnea nodulosa (part of holotype). Somewhat swollen branches. Rule=l cm.


Tubercles numerous, orbicular or linear to effigurate, becoming verrucose. Pseudocyphellae 

at apices of tubercles. Isidia absent to sparse. Soralia absent. Apothecia 

usually present. Spores ellipsoid, 8-11x5-7 jam. Conidia lageniform, 7-10 um. 

Chemistry: Usnic and constictic acids, undetermined substance becoming pink 

with sulphuric acid. For chemistry see Table 11. 

TABLE 11. Numbers of localities for chemotypes of Usnea nodulosa 

Chemotype 


localities 

constictic +' pink unknown' 

stictic ± constictic + norstictic +' pink unknown' 

stictic — constictic 

stictic — fatty acid 

salazinic -,-' pink unknown' 

The most distinctive characters of this species are the effigurate or linear tubercles 

and the very lax medulla; the chemistry is also usually a help. In a number of specimens 

the frequency of lateral branches as compared with those produced by isotomic 

dichotomy is relatively high, but it must be admitted this is not a clear-cut character. 

The cortex is very thin, sometimes has foveoles which become perforate, and often 

shows a 'bloom.' The efRgurate tubercles are like those of Usneapicta but smaller. 

It is possible that Usnea nodulosa is conspecific with U. hispida Mot. The holotype 

FIG. 9. Usnea nodulosa (part of holotype). Numerous papillae and tubercles, some of irregular 

form. Rule=l mm.


of the latter was in B and is presumed lost. We have not found an isotype, but in his 

description of the species Motyka (1936-38: 589) cited a plant which can be 

identified as Welwitsch, her angolense no. 72. The specimens of this number in BM 

are morphologically close to the East African plants assigned to U. nodulosa. They 

contain stictic acid, a fatty acid, and an undetermined substance (not the 'pink 

unknown')- Another specimen cited by Motyka, Braun 606 (from Kamerun), is 

also close to the East African plants morphologically. It contains stictic and norstictic 

(trace) acids. All these plants may be part of a widespread aggregate characterized 

by a tendency to lateral rather than isotomic dichotomous branching, irregularly 

shaped tubercles, and the stictic-constictic-norstictic group of depsidones. But 

owing to the differences between the specimens from East and West Africa and to 

the lack of type material we prefer not to choose a neotype from the West African 

specimens but to describe this new species from the plentiful East African material. 

A plant which appears to represent the isidiate counterpart of this species has been 

collected (2U 16/10) in which effigurate papillae are largely replaced by pseudocyphellae 

which have become secondarily sorediate, and many of these soralia 

contain isidia or spinules. It contains constictic acid, traces of Pcaperatic acid and 

of galbinic acid, and the 'pink unknown'. The specimen was collected in Uganda, 

Ankole District, Igara County, Kalinzu Forest, not far from several of the localities 

for Usnea nodulosa. Though it probably represents an undescribed species, the 

collection is too limited to base a description on it. 

East African specimens examined: Kenya: Rift Valley Province, Kericho District, Sambret- 

Timbilil SW Mau Forest, Kerfoot 2813 (EA). Eastern Province, Machakos District, lava 

flow 5 km NW of Kibwezi, 2K 22/20,141,3K 23j 9,14,157. Coast Province, Mamessa between 

Duruma and Taita, Hildebrandt 2357 (M).—Uganda: Masaka District, Buddu (Bukoto) 

County, N edge of Malabigambo Forest, 3U 2513; Jubiya Forest, 3U 32j5 (type collection), 

Lye L 121, L 613 (hb. Lye); 2 km NW of Bale, by Lake Nabugabo, Lye L 133 (hb. Lye); Sese 

County, Bugala Island, 3U 3013. East Mengo District, Kyagwe County, Kome Island, Lye 

L 3 (hb. Lye). Mubende District, Buwekula County, Lye L 156 (hb. Lye). 

11. Usnea perhispidella Steiner 

See Swinscow and Krog (1975: 133, plate 5A-B). 

12. Usnea perplexans Stirton 

Scott. Nat. 6: 103 (1881); Trans. Proc. New Zealand Inst. 30: 388 (1898) [' 1897']; type: India, 

Himalayas, Pengi, Watt (GLAM—holotype). Chemistry: Usnic and salazinic acids. 

Usnea barbata var. pulverulenta Mull. Arg., Flora, Jena 68: 499 (1885).—U. pulverulenta 

(Mull. Arg.) Mot., Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 107 (1936); type: Bagla, 

Abessinien, 7500 ft, 1885, Hildebrandt 308 p.p. (G—holotype!). Chemistry: Thalli a and c in 

packet, usnic and barbatic acids; thallus b usnic and salazinic acids. 

Thallus as in Usnea abissinica, except that the base is pale in most specimens, and 

slightly blackened in a few (including the type). Apothecia and pycnidia not seen. 

Chemistry: All specimens contain salazinic acid as the main depsidone except that 

part of the type of U. pulverulenta has only barbatic acid. Accessory substances, the 

commonest of which is barbatic acid, are shown in Table 7. The 'pink unknown' is 

referred to in the section on Chemistry above (p. 210). 

It is possible that our material represents more than one secondary species, for 

its range of altitude (Table 6) is unusually wide for the sorediate group, and the 

chemistry is somewhat complex.


East African specimens examined: Ethiopia: Begemder Province, Simien (Semen), Geech 

Camp, Tapper 3 (BM); W of Geech, Tapper 118 (BM); Chenek, Tapper 230 (BM). Bale, 

Dinshu Hill, Tapper 944b (BM); Gaysay summit, Tapper 640 (BM); Tapper 1102a (BM).— 

Kenya: Rift Valley Province, Elgeyo Marakwet District, Cherangani Hills 20 km S of Labot, 

2K 71505, 506; Trans Nzoia District, near Hoey's Bridge, 2K 12j8a; Laikipia District, near 

Naro Moru River Lodge, K 24/llb, 2K 34\6. Central Province, Nyeri District, Aberdare 

Mountains, by River Kinaini, 5K 12)17; Mt Kenya by Naro Moru track, K 33/4-1; Kiambu 

District, 8 km SE of Limuru, K 19J6, Burnet AMB 35 (BM). Eastern Province, Meru 

District, Mt Kenya N slope, Sirimon track, 4K 20)108, HJc, 4K 22)107. 

13. Usnea picta (Steiner) Mot. (Figs 10-11) 

Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2: 325 (1937).—Usnea ceratina var. picta Steiner, 

Sber. Akad. Wiss. Wien, math.-nat. Kl. 106 (1): 210 (1897); type: Brit. O-Afrika, Matchakos, 

1896, von Liechtenstein & Pospischill, (WU—holotype!). Chemistry: Usnic and salazinic acids. 

Thallus fruticose, non-pigmented, with pale base. Branches tapered, usually 

scrobiculate and here and there ridged, stiff and robust. Spinules sparse. Papillae 

sparse to none. Tubercles numerous, large, some efngurate, becoming verrucose. 

Pseudocyphellae on apices of tubercles. Isidia absent to sparse. Soralia absent. 

Apothecia usually present. Spores 10-13 x 6-8 um. For chemotypes see Table 12. 

TABLE 12. Numbers of localities for chemotypes of Usnea picta 

Chemotype 


localities 

salazinic ± constictic it norstictic 6 

protocetrariciprotocetraric aggregate 5 

stictic 1 

The distinguishing features are the stiff branches and the large, often efngurate 

or linear tubercles. Well developed thalli form robust shrubs up to about 15 cm high 

with many apothecia. 

This species favours the branches of fully exposed low trees and shrubs at about 

1500-1800 m altitude on hillsides and in open valleys. 

East African specimens examined: Ethiopia: Begemder Province, 40 km NE of Gondar, 

1962, Crees 4)34 (BM): doubtful determination.—Kenya: Rift Valley Province, Nakuru 

District, entrance to Masai Gorge near Lake Naivasha, K 30)120, 121. Eastern Province, 

Machakos District, Lukenia, 3K 1)4, 5K 1)24; Ol Doinyo Sapuk, 2K 2)23; Kilima Kiu, 

K 54)3, 4a, 13, 40. [The holotype also came from Machakos District, exact locality unstated.] 

Rift Valley Province, Laikipia District, Burgiiret, 4K 25)107.—Tanzania: Northern Province, 

Arusha District, Arusha National Park, Juniper Hill, T 3)5. Southern Highlands Province, 

Iringa District, Image Mountain, /. N. Bjornstad 787 (O). 

14. Usnea pulvinata Fr. 

See Swinscow and Krog (1976a: 29, fig. 4). 

Usnea barbata var. amblyodada Mull. Arg. was listed as a synonym of U.pulvinata. 

Review of the type specimens has cast some doubt on this decision and it may 

represent a separate species.

FIG. 10 Usnea picta (3K 1/13). Robust branches and numerous spinules. Rule=l cm.


FIG. 11. Usneapicta (3K 1/13). Numerous large tubercles, some of irregular form, among the 

spinules. Rule=l mm. 

15. Usnea roseola Vainio (Figs 12-13) 

Bot. Mag., Tokyo 35: 46 (1921); type: Japan, Prov. Rikuzen, Sendai, in arbore, 22 June 1913, 

Yasuda 138 (TUR-VAIN 00875—holotype!). Chemistry: Usnic, diffractaic, and barbatic 

(trace) acids, pigment. 

Thallus fruticose, pigmented, with pale base. Pink pigment mainly periaxial in 

medulla. Branches tapered, terete. Spinules sparse. Papillae few. Tubercles 

numerous. Pseudocyphellae numerous, many on apices of tubercles, also many 

punctiform on plane cortex, often becoming sorediate. Isidia numerous on cortex 

and on pseudocyphellae. Primary soralia numerous, excavate to plane or protuberant. 

Apothecia and pycnidia not seen. 

The distinguishing features of this species are the 'strawberry ice cream' pink 

pigment in the inner part of the medulla round the axis; the chemistry, diffractaic 

dz barbatic (trace) acids; and the presence of primary as well as secondary soralia 

and of isidia. In addition to Japan and now East Africa this species has been 

collected in Tristan da Cunha (1938, Christophersen, O!) and is listed by Jorgensen 

(1977) under 'Usnea aff. ceratina Ach.' (p.p.).The chemistry is the same at all 

these localities. 

Usnea mutabilis Stirton (GLAM—holotype!; BM—isotype!), a species found in 

the south-east U.S.A., differs in having a slightly redder pigment and containing, 

in addition to usnic acid, a series of fatty acids with Rf values intermediate between 

those of protolichesteric and caperatic acids. If soralia develop in this species, 

they appear to be of a secondary type on pseudocyphellae, whereas U. roseola has 

excavate soralia developing ab initio as well as those of secondary type. Coarse,


X, 

2


FIG. 13. Usnea roseola (4K. 6/123). Numerous pseudocyphellae, soralia, and isidia. Rule=l mm. 

prominent tubercles are also a feature of U. roseola but not of U. mutahilis. However, 

these characteristics of U. roseola are not well shown by the type specimen, which is 

poorly developed. 

In East Africa Usnea roseola grows on exposed trees and shrubs. The two localities 

where it has been collected are at 1450 and 1850 m on fairly dry but mist-affected 

hills. 

East African specimens examined: Kenya: Eastern Province, Marsabit District, Mt Marsabit 

near Lake Paradise, 4K 6/122,123. Eastern Province, Machakos District, Kilima Kiu, K 54/9. 

16. Usnea rubicunda Stirton (Fig. 14) 

Scott. Nat. 6: 102 (1881); type: England [two thalli on one sheet], Holmes (BM—holotype!). 

Chemistry: Usnic, stictic, constictic and norstictic (trace) acids. 

Usnea sublurida Stirton, Scott. Nat. 6: 102 (1881); type: Scotland, N[ew] Galloway, J. 

M'Andrew 15 (BM—holotype!). Chemistry: Usnic, stictic, constictic, and norstictic acids. 

Usnea rubrotincta Stirton, Scott. Nat. 6: 103 (1881); type: Madeira, Funchal, Joe Payne 

(BM—holotype!). Chemistry: Usnic, salazinic, and norstictic acids. 

Usnea rubescens Stirton, Scott. Nat. 7: 76 (1883); type: Australia, New South Wales, 

Hawavra, Kirton [left-hand specimen] (BM—lectotype selected James (1979)!). Chemistry: 

Usnic, stictic, and norstictic (trace) acids. 

Thallus fruticose to subpendulous, with red pigment in cortex and pale base. 

Branches tapered, terete. Spinules and fibrils often numerous, giving a bristly 

appearance to branches. Papillae sparse or absent. Tubercles numerous. Pseudocyphellae 

on tubercles and punctiform on plane cortex. Isidia produced on cortex 

and from pseudocyphellae. Soralia absent, but in some specimens pseudocyphellae


FIG. 14. Usnea rubicunda (K 33/3a). Large straggling thallus as commonly seen in East Africa. 

Rule=l cm.


become sorediate. Apothecia rare (present in 5K 7/13). Spores 8-10x5-7 um. 

Pycnidia not seen. For chemistry see Table 13. 

TABLE 13. Numbers of localities for chemotypes of Usnea rubicunda 

Chemotype 


localities 

stictic acid aggregate ± norstictic (trace) 8 

salazinic + norstictic ( + galbinic in one thallus) 18 

fatty acids 2 

Studies by James (1979) have shown that Usnea rubiginea (Michaux) Massal., is 

not the correct name for this species. 

The form of the thallus varies from a more or less rounded shrub to a straggling 

bundle of branches up to about 25 cm long. The pseudocyphellae may vary from 

sparse to numerous, and from punctate to effigurate and confluent, and produce 

soredia, isidia, and spinules. Likewise the production of isidia on the cortex is very 

variable. 

The commonest chemical race in East Africa is a combination of salazinic and 

norstictic acids. The same race has been reported in Japan (Asahina, 1965) and is 

known rarely in the British Isles (James, 1979). But at about a third of the localities 

in our area plants have been found with stictic and norstictic acids as in the type. 

At two localities plants were found containing only fatty acids in addition to usnic 

acid. No morphological differences between any of the races could be detected. 

The pigment in this species is always in the cortex, whereas in Usnea sorediosula 

it is always in the medulla. The two species also differ chemically, in that U. 

sorediosula always contains protocetraric acid, which has not so far been found in 

U. rubicunda. Macroscopically the two species closely resemble each other and 

sometimes grow mixed. 

Rather widespread in East Africa, Usnea rubicunda usually grows on the trunks 

and large branches of trees in sheltered places, but also occasionally on rocks in the 

grassy banks of tracks. It is commonest at about 1500-2500 m. 

East African specimens examined: Ethiopia: Near Bagla, 1906, Gallina (KGY)—Kenya: 

Central Province, Nyeri District, Mt Kenya E side, K 3313a, 3d, 5a; Kirinyaga District, Mt 

Kenya near Castle Forest Station, K 49jl9c, 5K 7/13, 18; Mt Kenya near Kamweti Forest 

Station, K 50J9, 10-lb, lie; Mt Kenya, shady valley 2 km N of Castle Forest Station, 

K 51 j34a; Mt Kenya, S of Castle Forest Station, 5K 6120. Rift Valley Province, Laikipia 

District, near Naro Moru River Lodge, K 24j 9, 2K 34)5. Eastern Province, Marsabit District, 

Mt Marsabit near Lake Paradise, 4K 6/104-106, Lye L 646, W side of Sokorte Dika ' swamp 

lake', Lye L 662 (both hb. Lye); Mem District, Mt Kenya E side at Themwe, 3K 16)18, 58, 

83; Machakos District, Kilima Kiu, K 54j 15b, Ol Doinyo Sapuk, 2K 2125. Coast Province, 

Taita District, WofWundanyi, 2K 26J6.—Tanzania: Northern Province, Arusha District, 

Arusha National Park, Juniper Hill, T 3163, near Ngurdoto Gate, T 6'/'8a; Moshi District, 

intersection of Marangu-Mandara Hut track with boundary of Kilimanjaro Forest Reserve, 

Burnet 169a (BM). Southern Highlands Province, Rungwe District, SW foothills of Mt 

Rungwe, T. Pocs et al. 6758jE (hb. Pocs).—Uganda: Ankole District, Bunyaruguru County, 

7 km NW of sawmill W of Rubuzigye, Lye L 181 (hb. Lye). Kigezi District, Kinkizi County, 

edge of Impenetrable Forest, 3U 54J4, 3U 55/1, 3b; Rubanda County, 2 km W of Burimbe, 

3U48/2, above Rubanda, Burnet 211 (BM).


17. Usnea ruwenzoriana Mot. (Fig. 15) 

In Zahlbruckner and Hauman, Mem. Inst. r. colon, beige, Sect. Set. nat. mid. 5: 27 (1936); 

type: Congo Beige, Ruwenzori, etage alpin, association des lichens sur branches de Philippia, 

4000 m, juillet-aout 1932, L. Hauman (S—isotype!). Chemistry: Usnic and alectorialic acids. 

Usnea ruwenzoriana var. nigroapiculata Mot., in Zahlbruckner and Hauman, Mem. Inst. r. 

colon, beige Sect. Sci. nat. mid. 5: 28 (1936); type: Ruwenzori, 4200 m, sur Helichrysum, 

juillet 1932 L. Hauman 953 (BM—isotype!). Chemistry: Usnic acid. 

Usnea irregularis Mot., Annh Univ. Mariae Curie-Sklodowska, C, 11: 115 (1959) ['1956']; 

type: Muhavura-sattel 3000 m/M, Hypericum Stamme u. Aeste ringsum gleichstark bewachsen 

(BERN—holotype!). Chemistry: Usnic, protocetraric, alectorialic and salazinic acids. 

FIG. 15. Usnea ruwenzoriana (5K 13/23a). Excavate soralia. Rule=l mm. 

Thallus as in Usnea abissinica with black base. Apothecia and pyenidia not seen. 

Chemistry: Most specimens contain both alectorialic and protocetraric acids, but a 

few contain one or the other (Table 7). 

This species has the most consistently black base of all the sorediate species. 

East African specimens examined: Kenya: Central Province, Nyeri District, Mt Kenya W 

side, ericaceous zone, 2K 36140, 47, 48; Aberdare Mountains SE of Lesatima, 5K 13123a. 

Eastern Province, Meru District, Mt Kenya N slope, Sirimon track, 4K 231107.—Uganda: 

Kigezi District, Bufumbira County, Muhavura N side, U 13/503-2, 3U 61j505-2b, 508- 

18. Usnea sanguinea Swinscow and Krog sp. nov. (Figs 16-17) 

Thallus fruticosus, pigmento rubro in cortice instructus. Rami gradatim contracti, teretes. 

Spinulae moderate densae. Papillae et tubercula numerosa. Pseudocyphellae sparsae, praecipue 

ad apices papillarum. Apothecia plerumque adsunt. Acidum usnicum, acidum salazinicum, et 

acidum norsticticum continens. 

Typus: Tanzania, Northern Province, Arusha District, Arusha National Park, Juniper Hill, 

3 14'S, 36=51'E, 1500 m altitude, on trees and shrubs, 1974, Swinscow & Krog T3I16(BM— 

holotypus; O—isotypus).

244 THE LICHENOLOGIST Vol. 11


FIG. 17. Usnea sanguinea (part of holotype). Numerous tubercles and papillae. Rule=l mm. 

Thallus fruticose, with red pigment in cortex, pale base. Branches tapered, terete. 

Spinules moderately dense. Papillae sparse to numerous. Tubercles numerous. 

Pseudocyphellae on apices of tubercles and also punctiform on plane cortex. Isidia 

absent to sparse. Soralia absent. Apothecia usually present. Spores 9-10x6-7 um. 

Conidia lageniform, 8-10 um. Chemistry: Usnic, salazinic and norstictic acids. 

The distinguishing features of this species are the red pigment within the cortex 

and the numerous papillae and tubercles. Usnea subflorida, the only other pigmented 

primary species in our area, is differentiated by having most of its pigment in the 

medulla just below the cortex. 

East African specimens examined: Tanzania: Northern Province, Arusha District, Arusha 

National Park, Juniper Hill, T 3116 (holotype); valley by Seneto Pool, T 8110; Mt Meru W 

side, T 12! 136. 

19, Usnea sorediosula Mot. 

See Swinscow and Krog (1975:134, plate 6). 

20. Usnea subeciliata (Mot.) Swinscow and Krog comb. nov. 

Usnea pulverulenta f. subeciliata Mot., in Motyka and Pichi-Sermolli, Webbia 8: 388 (1952); 

type: [Ethiopia], Semien-Poco a monte del villaggio di Nori, m 3700 circa, 10 April 1937, 

R. Pichi-Sermolli 2816 p.p. (FI—lectotype, designated here!). Chemistry: Usnic acid, fatty 

acids with/?/values between those of caperatic and protolichesteric acids, salazinic acid 

(trace). 

Thallus as in Usnea abissinica, except that the base is usually pale, as in the 

lectotype, but occasionally slightly blackened. Apothecia and pycnidia not seen.


Chemistry: All specimens contain fatty acids; salazinic acid is accessory in some 

specimens, and one has norstictic acid also accessory (Table 7). 

East African specimens examined: Ethiopia: Bale Province, mountain pass between Adaba 

and Goba, E 22/69, 70; 2 km E of Little Bam, Tapper 995a (BM); below Little Batu, Tapper 

656 (BM); below Likumsa, Tapper 718a (BM); Mt Orobo lava flows, Saneti end, Tapper 

764b (BM); Mt Orobo, Tapper 774 (BM); Walla lava flows, Tapper 1114 (BM); Gaysay 

summit, Tapper 1101 (BM). Arussi Province, E of Asella, E 31/35. Begemder Province, 

Simien (Semen), Sankaber to W of camp, Tapper 162a (BM); Chenek, Tapper 219c (BM); 

Tillik Amba, Tapper 269 (BM).—Kenya: Eastern Province, Meru District, Mt Kenya N 

slope, Sirimon track, 4K 20/102,4K 21101b. 

21. Usnea subflorida (Zahlbr.) Mot. (Fig. 18) 

Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2: 335 (1937).—Usnea steineri var. subflorida 

Zahlbr., in Engler, Bot.Jb. 60: 541 (1926); type: Deutsch Ostafrika; an Baumen bei Meru, 

1908, Fassmann(WnO73—lectotype, designated here!);W7067 pp.—isolectotype!). Chemistry: 

Usnic, protocetraric, protocetraric aggregate, and salazinic acids, pigment. 

Usnea medio-africana Dodge, Ann. Mo. bot. Gdn 43: 393 (1956); type: Uganda, Kigezi, 

Mafuga, 7500 ft, on trees, 1947, Dale 41 p.p. (BM—lectotype, designated here; that part of the 

material with a solid axis and excluding the branch of Usnea pulvinulata Dodge also present!). 

Chemistry: Usnic, protocetraric, and ?trace salazinic acids, pigment. 

Usnea dichroa Mot., Annls Univ. Mariae Curie-Sklodowska, C, 11:118 (1959) [' 1956']; type: 

Kraterboden des Nyamuragira, 2957 m/M, am Grunde der Ericaceenstammchen, in reichlichen 

Usnea Bestanden, 29 August 1954, Stauffer 3124/259 (BERN—holotype!). Chemistry: 

Usnic, protocetraric, and barbatic acids, pigment. 

FIG. 18. Usnea subflorida (4K 20/103). Black base arrowed. Rule=l cm.


Thallus fruticose, with red to ochraceous pigment usually subcortical in medulla 

and also in cortex, occasionally only in cortex, base black. Branches tapered, terete. 

Spinules sparse. Papillae and tubercles numerous. Pseudocyphellae on tubercles. 

Isidia absent to sparse. Soralia absent. Apothecia usually present. Spores 10-14 x 

6-9 urn. For chemotypes see Table 14. 

TABLE 14. Numbers of localities for chemotypes of Usnea subflorida 

Chemotype 


localities 

protocetraric — barbatic* ~ protocetraric aggregate 20 

norstictic ± barbatic* 2 

salazinic = barbatic* 1 

* In apothecia only. 

The distinguishing features of this species are the subcortical pigment in the 

medulla and the numerous papillae and tubercles. In some thalli the amount of 

pigmentation may be no more than a patch here and there (p. 209). Usnea sanguinea 

has the pigment restricted to the cortex. U. subflorida, like U. bicolorata and U. 

sorediosula, usually contains protocetraric acid. The barbatic acid commonly 

found has been detected only in the apothecia. 

This is mainly a species of high montane forest and grows especially abundantly 

on the twigs and small branches of the tree canopy. 

East African specimens examined: Ethiopia: Bale Province, Bale Mountains National Park, 

Tapper 626c (BM).—Kenya: Central Province, Nyeri District, Mt Kenya W side, K 10j 19, 

Kll\7,K 2816, K 31)32, K 34! 103a, 2K 25121, 24, 29, 32,140, 2K 36)32, Lye L 303 (hb. Lye); 

Aberdare Mountains E of Lesatima, K 26\8b, 27a, 104,136, 5K 9/29; Wandera track summit, 

Agnelli s.n. Central Province, Kirinyaga District, Mt Kenya, 2 km NW of Irangi Forest 

Station, K 48!22. Rift Valley Province, Trans Nzoia District, E side of Mt Elgon, Hamilton & 

Wendelbo s.n., 1967, Ketner-Oostra 1906c; Elgeyo Marakwet District, Cherangani Hills 

20 km S of Labot, 2K 71524b. Nyanza Province, Kisumu-Londiani District, Tinderet Forest 

Reserve, Maas Geesteranus 11203, 10952 p.p., [Almborn, Lich. afr. no. 41, sub Usnea scutata 

Mot.] (BM). Eastern Province, Meru District, Mt Kenya, Themwe, 3K 16/11, 28, 34, 51c, 

528; Mt Kenya, N slope by Sirimon track, 4K 201103, 104,109a, 111b, 112, 113, 4K 24)105.— 

Tanzania: Northern Province, Arusha District, Arusha National Park, Juniper Hill, T 3135; 

Mt Meru crater, T 5)38; Mt Meru W side, T 13)19. Southern Highlands Province, Mbeya 

District, between Kimondo and Kikondo, 1978, Dahl s.n. (O). 

22. Usnea submollis Steiner (Figs 19-20) 

Verh. zool.-bot. Ges. Wien 53: 229 (1903); type: Kamerunpik, Gipfelregion bei 36-4000 m, 

March 1898, Bornmuller (WU—holotype!). Chemistry: Usnic and alectorialic (trace in 

apothecium) acids. 

Usnea obtusata f. perstrigosa Mot., in Motyka and Pichi-Sermolli, Webbia 8: 391 (1952); 

type: [Ethiopia], Pianura di Dukulcan Jesus (Alefa), 2200 m, 1937, Pichi-Sermolli 2756 (FI— 

holotype!). Chemistry: Usnic and salazinic acids. 

Usnea obtusata f. perflava Mot., in Motyka and Pichi-Sermolli, Webbia 8: 392 (1952); 

type: [Ethiopia], presso la chiesa di Sciaura Mariam Alefa, 2200 m, Pichi-Sermolli 2757, 

(FI—lectotype, designated here!).Chemistry: Usnic, salazinic, and alectorialic (in apothecia) 

acids.


Usnea permira Mot., Annls Univ. Mariae Curie-Sklodowska, C, 11: 137 (1959) ['1956']; 

type: Gipfel des Mgahinga, 3470 m/M, Ericaceenbiisch, 15 November 1954, Stauffer 3277J 

799 (BERN—holotype!). Chemistry: Usnic, salazinic, and alectorialic (in apothecia) acids, 

fatty acids with Rf values between those of caperatic and protolichesteric acids. 

Thallus fruticose, non-pigmented, with pale base. Branches often fusiform, 

terete. Spinules sparse. Papillae and tubercles numerous. Pseudocyphellae on 

tubercles. Isidia absent to sparse. Soralia absent. Apothecia usually present. 

Spores 10-13 x 7-8 |.im. For chemical races see Table 15. 

TABLE 15. Numbers of localities for chemotypes of Usnea submollis 

Chemotype 


localities 

alectorialic* 

salazinic + alectorialic* —fatty acids 

salazinic zizgalbinic (trace) 

total salazinic/alectorialic 

norstictic 

stictic + barbatic* 

usnic acid only 

* In apothecia only. 

3 

20 

13 

36 

2 

1 

2 

Nearly all plants of Usnea submollis contain salazinic acid, and most in addition 

have alectorialic acid in the apothecia. A collection of thalli from the ericaceous 

zone on Muhavura in Uganda at about 3000 m contains norstictic acid instead of 

salazinic acid and lacks alectorialic acid; it resembles a stunted form of this species. 

The distinguishing morphological features of Usnea submollis are the numerous 

papillae densely arranged, few spinules, and sometimes rather swollen branches 

with a lax medulla. For differentiation of this variable species or aggregate from 

U. complanata see p. 212, and from U. albomaculata see p. 214. U. picta has larger 

tubercles, relatively fewer papillae, and on average a thicker cortex (Table 3). 

Usnea fruticosa Stirton, U. robusta Stirton, U. splendens Stirton, U. thomsonii 

Stirton, and U. thomsonii subsp. arborea (Stirton) Mot. are a group of taxa 

(BM—holotypes!) from the Himalayas and possibly represent a single species. 

They are close to U. submollis but stiffer and generally with larger tubercles. 

Usnea submollis is common from about 2000 to 3500 m in montane forest and up 

into the ericaceous zone, growing on trees and shrubs by tracks and in glades. 

East African specimens examined: Ethiopia: Sidamo Province, 6km NW of Wadera, 

E 10114; SE of Hagere Selam, Winnem 586 (O); NE of Kebre Mengist, Winnem 587 (O). 

Bale Province, mountain pass between Adaba and Goba, E 22/71, Winnem 356 (O); 24 km E of 

Adaba, E 23)15, Winnem 367 (O); near Ukumsa, Tapper 1072 (BM). Gemu Gofa Province, 

Gidole, Winnem 638 (O). Arussi Province, E of Asella, E 30)68, Mt Chilalo, Winnem 752 (O). 

Shewa Province, Menegesha, Tapper 544 (BM). Harerge Province, Harer, S face of Gara 

Mullata, Burger 3137 (BM).—Kenya: Eastern Province, Marsabit District, Mt Marsabit, 

4K 61109-113; Meru District, Mt Kenya N slope by Sirimon track, 4K 23/108, 4K 24/107; 

Machakos District, Mua Hills, K 5/33a. Rift Valley Province, Elgeyo Marakwet District, 

Cherangani Hills 20 km S of Labot, 2K 7/524a; 10 km S of Labot, 2K 8/116. Central Province, 

Nyeri District, Aberdare Mountains by River Kinaini, 5K12/19; Mt Kenya W side, K 33jib,

19 Usnea submollis (3K 16/36). Somewhat swollen branches, few spinules, numerous fibrils. Rule=l cm.


FIG. 20. Usnea submollis (3K 16/36). Dense papillae. Rule=l mm. 

117, 2K 33/28; Kirinyaga District, 2 km N of Castle Forest Station, K 51j25a.~Tanzania: 

Northern Province, Arusha District, Arusha National Park, Juniper Hill, T 3/9a; Mt Meru 

crater, T 5/7; by Seneto Pool, T 8113, 15. Eastern Province, Morogoro District, Kitulangala 

Forest, Dahl s.n. (O). Southern Highlands Province, Mbeya District, Rungwe Volcano, 

Pocs 6507/1 (BM).— Uganda: Karamoja District, Matheniko County, Mt Moroto near 

Sogolomon, 2U 36/51b-l, 2U 36/61-la, 61-3. Bugisu District, North Bugisu County, Mt 

Elgon, by Sasa Hut, 2U 44157, Manum s.n. (hb. Swinscow). Kigezi District, Bufumbira 

County, Muhavura N side, U16/20-1, 3U 61/505, 506. 

23. Usnea undulata Stirton 

See Swinscow and Krog (1975:123, plate 1A,B). 

The following species is here reduced to synonymy with Usnea undulata: 

Usnea hispidula (Mull. Arg.) Zahlbr., Cat. Lich. Univ. 6: 581 (1930).—Usnea barbata var. 

hispidula Mull. Arg., Bot.Jb. 20: 245 (1894); type: Lich. usamb. no. 29, Usambara, D.O. Afr. 

1894, Hoist 764 (G—holotype!). Chemistry: Usnic, psoromic, and conpsoromic acids. 

The type is a straggling thallus with basal trunk but lacking a holdfast, bearing 

punctiform pseudocyphellae along the branches. Isidia are numerous on the 

pseudocyphellae and present also on the cortex. This is the first specimen of Usnea 

undulata to be seen containing psoromic acid. Its presence is to be expected in this 

species if the inference is correct that U. undulaia is derived from the U. complanata 

aggregate, in which psoromic acid is common. 

Summary 

Twenty-three fruticose species of Usnea subgenus Usnea are recognized for East 

Africa. They include two species described as new, Usnea nodulosa and U. sanguinea


spp. nov. The main characters found useful in the differentiation of the fruticose 

species of Usnea were pigmentation and type of propaguks produced. Subsidiary 

characters of importance included the mode of branching, relative frequency of 

spinules and papillae or tubercles, and chemistry. Taxonomic and ecological data 

are provided on 15 of the species, while 8 species, which have been discussed in 

previous papers, are more briefly reviewed. Many taxa are reduced to synonymy, 

and a key is provided. 

For the loan of specimens we are grateful to Dr A. D. Q. Agnew, Mrs I. N. BJ0rnstad, Miss 

A. M. Burnet, Dr E. Dahl, Dr A. C. Hamilton, Mrs R. Ketner-Oostra, Mr K. A. Lye, Dr A. 

Pentecost, Dr T. Pocs, Mr L. Ryvarden, Dr R. C. Tapper, Dr P. Wendelbo, and Miss B. 

Winnem; and to the following institutional herbaria: BERN, BM, FI, G, GLAM, L, M, S, 

TUR, UPS, W, WU. We especially thank Professor Dr R. Santesson for selecting and sending 

on loan from S specimens in Motyka's ' Collectio Usnearum, Collectio cotypica unica.' 

T. D. V. S. gratefully acknowledges the receipt of grants from the Royal Society and the 

Linnean Society of London. H. K. gratefully acknowledges the receipt of grants from NORAD 

and the Norwegian Research Council for Science and the Humanities. 

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Asahina, Y. (1965) Lichenologische Notizen, § 197. J. Jap. Bot. 40: 129-133. 

Bertsch, K. (1962) Flechten (Lichenes, Usneaceae) aus Tanganjika. Stung. Beitr. Naturk. 

84: 1-6. 

Culberson, C. F. (1972) Improved conditions and new data for the identification of lichen 

products by a standardized thin-layer chromatographic method. J. Chromat. 72: 113-125. 

Culberson, C. F. and Kristinsson, H. (1970) A standardized method for the identification of 

lichen products. J. Chromat. 46: 85-93. 

Dodge, C. W. (1956) Some lichens of tropical Africa. II. Usnea. Ann. Mo. bot. Gdn 43: 381- 

396. 

Dodge, C. W. (1957) Some lichens of tropical Africa. II. Usnea (continued). Ann. Mo. bot. 

Gdn 44: 1-76. 

James, P. W. (1979) Notes on Usnea rubiginea and U. rubicunda. Lichenologist 11: 322-323. 

J0rgenson, P. M. (1977) Foliose and fruticose lichens from Tristan da Cunha. Norske Vidensk- 

Akad. 1. Mat.-Naturu. Kl.,n.s.36-. V-4O. 

Menlove, J. E. (1974) Thin-layer chromatography for the identification of lichen substances. 

Bull. Br. Itch. Soc. 34: 3-5. 

Motyka, J. (1936-38) Lichenum Generis Usnea Studium Monographicum, Pars Systematica. 

Leopoli: privately printed. . 

Motyka, J (1952) In Motyka, J. and Pichi-Sermolli, R. Usneae in missione ad Lacum Tana 

et Semien a R. Pichi-Sermolli anno 1937 lectae. Webbia 8: 383-404. 

Motyka, J. (1959) ['1956'] Die Flechtengattung Usnea Wigg. lm Virunga-Gebiet (Zentral- 

Afrika). Annls. Univ. Mariae Curie-Sklodowska, C, 11: 103-150. 

Motyka, J. (1961) Usneae a R.A. Maas Geesteranus in Africa orientali et australi anno 1949 

collectae. Persoonia 1: 415-431. 

Stein, B (1888) Ueber afrikanische Flechten. Jber. schles. Ges. vaterl. Kult. bb: 133-14A 

Steiner, J. (1897) Flechten aus Britisch-Ostafrika. Sber. Akad. Wiss. Wien, math.-nat. Kl. 

106' 207—234 

Stizenberger, E. (1890-91) Lichenaea africana. Fasc. I. Ber. Tat. St Gall, naturw. Ges. 

1889/90: 1-144. 

Swinscow, T. D. V. and Krog, H. (1975) The Usnea undulata aggregate in East Alrica. 

Lichenologist 7: 121-138. 

Swinscow, T. D. V. and Krog, H. (1976a) The Usnea bornmuelleri aggregate in East Africa. 

Norm. J. Bot. 23:23-31. 

Swinscow, T. D. V. and Krog, H. (19766) The Usnea articulata aggregate in East Africa. 

Norw.J.Bot. 23:261-268. . . 

Swinscow, T. D. V. and Krog, H. (1978) Pendulous species of Usnea in East Africa. Norw.J. 

Bot. 25: 221-241.


Index to Taxa 

(Only main references are given) 

abissinica, 221 

albomaculata, 221 

anormalis, 229 

aristata, 225 

barbata var. amblyoclada, 236 

var. hispidula, 250 

var. pulverulenta, 235 

var. strigosa f. complanata, 229 

bicolorata, 227 

var. pseudorubescens, 227 

blepharoides, 223 

bornmuelleri, 229 

cacuminum, 229 

ceratina var. pz'cta, 236 

complanata, 229 

dichroa, 246 

var. virgulata, 227 

griseola, 227 

hispida, 234 

hispidula, 250 

incrassata, 232 

intumescens, 225 

irregularis, 243 

leprosa, 232 

maculata, 232 

magnifica, 229 

medio-africana, 246 

mutabilis, 238 

nodulosa, 232 

obtusata, 229 

f. perflava, 247 

f. perstrigosa, 247 

perhispidella, 235 

permira, 248 

perplexans, 235 

£icfti, 236 

pulverulenta, 235 

f. subeciliata, 245 

pulvinata, 236 

pulvinulata, 246 

roseola, 238 

rubescens, 240 

rubicunda, 240 

rubrotincta, 240 

rutilans, 232 

rwmenzoriana, 243 

var. nigroapiculata, 243 

sanguinea, 243 

simplicissima, 225 

sorediosula, 245 

steineri var. subflorida, 246 

subeciliata, 245 

subflorida, 246 

sublurida, 240 

submollis, 247 

undulata, 250 

vulcanorum, 232 

Accepted for publication 25 May 1979

The Fruticose Species of Usnea Subgenus Usnea in East Africa

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