Bulletin of the British Museum (Natural History)

LICHEN GENUS MICAREA IN EUROPE 101
the section. A positive reaction due to gyrophoric acid is seen as an orange-red front moving
across the section, with the colour quickly fading in its wake. If the concentration of gyrophoric
acid is very high than the reaction may be more immediate and intense, but, nevertheless, the
colour quickly fades away within a few seconds. A similar procedure should be followed when
testing for other colour changes.
The identification of Micarea species usually requires accurate measurement of the dimen-
sions of spores, conidia, and paraphyses, such that a microscope with a good resolution at
X 1000, coupled with a carefully calibrated measuring eyepiece, is invaluable, and in many cases
essential.
Spores should be observed and measured in 10% KOH; in most cases this solution will render
any septa visible. If, however, the spore contents are difficult to clear, septa can be discerned by
preparing an apothecial section or squash in LCB and heating (just to boiHng) over a spirit lamp;
any septa should then be clearly seen, especially under oil-immersion (xlOOO).
Conidia should always be examined under oil-immersion (at least xlOOO). Preparations can
be made in 10% KOH, but better resolution is obtained using ammoniacal erythrosin. In water,
small conidia are prone to 'Brownian movement', making alignment with the measuring
graticule a frustrating task! If conidia and conidiogenous cells are to be examined in a squash
preparation it is often helpful to soak an intact pycnidium in a small drop of 10% KOH on a shde
for about a minute; excess KOH is then soaked up with the edge of a piece of tissue-paper or
filter-paper and the squash prepared under a cover-slip in ammoniacal erythrosin. The KOH
softens the pycnidial wall and does not alter the effectiveness of the erythrosin.
Fine measurements, such as the width of spores, conidia, hyphae, and paraphyses should not
be made in LCB, this solution often causing much shrinkage; with hyphae and paraphyses the
cytoplasm (lumina) is intensely stained, but the delimitation of their outer walls is often difficult
to ascertain.
Key to European species
la Hymenium, atleast in upper part, dull greenish or brownish in water, K-l- violet [pigment D].. 2
lb Hymenium variously coloured or hyaline, not turning to violet in K (if purple in K, then
pigment already purplish in water [pigment C] 12
2a (la) Hypothecium dark purple-brown, K+ purple intensifying or K+ green in upper part.
Saxicolous 40. M. subviolascens (p. 185)
2b Hypothecium hyaline or pale . Usually corticolous or lignicolous 3
3a (2b) Spores mostly 3 (or more)-septate , or over 15 /u,m long 4
3b Spores mostly simple or 1-septate (2- or 3-septate spores if present very rare) , mostly less than
15 /am long
4a (3a) Apothecia sections and/or thallus C + orange-red (gyrophoric acid) 5
4b Apothecia sections and thallus C- [note: the K+ violet pigment also reacts C+ violet],
gyrophoric acid absent
5a (4a) Spores 0-l(-2)-septate, few exceeding 16 /xm in length. Usually lignicolous. Rare forms
of this very variable species 11. M. denigrata (p. 127)
5b Spores mostly 3 (or more)-septate, or many exceeding 16 /am in length. Usually on bark or
twigs
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6a (5b) Spores (l-)3-septate, fusiform, often curved, 10-17(-19)x2-5-3(-3-5) /am. Microconidia
(4-7-)5-5-7-5x0-8 /am; mesoconidia (3-)3-5-5(-5-7)x 1-1-5 /am; macroconidia some-
times present, curved 30. M. nitschkeana (p. 165)
6b Spores 0-3(-6)-septate, acicular, 13-26xl-5-2-5(-3) /am. Microconidia 3-8-5 xO-8-1 /am;
mesoconidia 3-6-5-3 x 1-1-4 /am; macroconidia unknown 14. M. globulosella (p. 134)
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