Bulletin of the British Museum (Natural History)

144 BRIAN JOHN COPPINS
incrassate and coloured with green or greenish brown pigment and then up to 3 /xm wide, usually
coherent (even in K) and, together with the surrounding pigmented matrix, form an epithecium.
Hypothecium c. 100-230(-350) /xm tall, dilutely pigmented with pigment confined to gel matrix;
upper part dull aeruginose or olive-brownish K- or + dulling, HNO3+ reddish); lower part
often without greenish tinge, and then being dilute brownish or ± hyaline; hyphae interwoven or
some ± vertically orientated near the hymenium, c. 1-1-7 /am wide; ascogenous hyphae with
short, swollen cells c. 2-5-4 /xm wide. Excipulum ± distinct in sections of young, hemispherical
apothecia, but soon becoming strongly reflexed and not sharply delimited from the hymenium,
dilute brown or sometimes darkish brown along the outer edge. Hypothecial and excipular
tissues sometimes elongated vertically to form a stipe ('f. gomphillaced')
Pycnidia inconspicuous, ± immersed, with walls green (K-, HNO3-I- red) in exposed upper
parts and ± hyaline in immersed lower parts; of three types [only type (c) is common]: (a) c. 100
ixm diam; conidia {macroconidia) curved or hamate, 0-3-septate, 16-22 Xc. 1 /xm; (b) c. 100-140
/xm diam; conidia (mesoconidia) ± cylindrical, oblong-ellipsoid, obovoid or oblong-obovoid,
usually distinctly truncate at proximal end, often 2-3-guttulate, 4-7(-7-6)xl-2-l-8 fxm; (c) c.
40-50 ^im diam; conidia (microconidia) narrowly cylindrical, only faintly truncated at proximal
end, eguttulate, (4-5-)5-7(-8)x 0-8-1 /xm.
Chemistry: Thallus K-, C-, KC-, PD-I- red; sections of apothecia C-, PD-; t.l.c:
argopsin.
Observations: Micarea lignaria is characterized by its whitish to grey, convex to ± globose
areolae which are PD+ red (argopsin; but see var. endoleuca), black, markedly convex to ±
globose apothecia, green upper hymenium, dilute greenish or dilute olive-brownish hypothecium,
'^nd 3-7-septate, fusiform spores. When on lignum the thallus is often reduced to small
scattered areolae and sometimes it is ± entirely endoxylic. The apothecia are less variable in
appearance, and pale (shade) forms are very rare. However, the apothecia are occasionally
found (especially on rock in dry underhangs) to be stipitate with a 'stipe' (composed of vertically
extended hypothecial and excipular tissues) up to 0-4 mm, or even 1 mm, tall (Fig. 3E). These
forms have been ascribed the status of form, variety, species and even genus, viz.: Nylander's
new species and genus Stereocauliscum gomphillaceum. In the type material of this, some
'stipes' are extremely tall (up to 1 mm) and composed of vertically proliferating apothecia, with
the apical apothecia being the youngest; the apothecia are immature (or arrested in their
development) with few asci and spores. In my opinion these stalked forms of A/, lignaria result
from abnormal development in response to adverse environmental conditions and are, there-
fore, not worthy of taxonomic recognition at any rank.
M. lignaria is often confused with M. cinerea and M. peliocarpa, but these two species have
usually more flattened and often paler apothecia, more richly branched paraphyses, and a
hyaline hypothecium. In addition, they contain gyrophoric acid, resulting in the C-l- orange-red
(quickly fading) , PD
— reactions of their thalli and apothecia. M. ternaria {q. v. ) is very similar to
M. lignaria, but has more flattened apothecia with a more discernible excipulum and spores
which are never more than 3-septate; furthermore, it lacks any lichen substances.
Habitat and distribution: M. lignaria occurs on a wide range of substrata, but is most common
in upland districts, growing over bryophytes or plant debris on siliceous rocks and walls, or on
exposed peaty ground. Associated lichens found in such habitats in Britain include
Arthrorhaphis citrinella, Baeomyces rufus, Cladonia coccifera, C. floerkeana, C. squamosa, C.
subcervicornis, Coelocaulon aculeatum s. lat., Lecidea granulosa, L. icmalea, Lecidoma demissum,
Lepraria neglecta, Micarea leprosula, M. peliocarpa, Ochrolechia frigida, Parmelia
saxatilis, and Pseudephebe pubescens. It often grows over bryophyte mats that are heavily
invaded by gelatinous algae, and in such situations in Scotland it has been found with the rare, or
overlooked, Arctomia delicatula and Belonia incarnata. When growing directly on rock M.
lignaria is mostly confined to sheltered, shaded situations and is sometimes present in the
Micareetum sylvicolae in rock underhangs. It is usually present in abundance in the old lead and
zinc mine workings of the Pennines and Scotland, where it grows over decaying bryophytes and
.