Bulletin of the British Museum (Natural History)

LICHEN GENUS MICAREA IN EUROPE 187
rather scanty, of two types: p.p. evenly distributed, irregularly flexuose, simple or sparingly
branched, often anastomosing, hyaline, thin, 0-7-1 /xm wide, sometimes widening above to 1-8
fim; p.p. fewer in number, as scattered individuals or in small fascicles, straight, simple or
occasionally forked above , stout, coated ± throughout (but most intensely so around the apices)
by dark green pigment and appearing c. 2-3 /xm wide, apices sometimes incrassate and up to 4
/Lim wide. Hypothecium 90-200 /xm tall, dark aeruginose or olive-black, K- or + green
intensifying; lower ('core') part, or rarely the entire hypothecium, dark purplish brown, K-lpurple
intensifying; all pigments HNO3+ purple-red; hyphae coated with dense dark green
pigment and 2-3 /xm wide (overall), interwoven but becoming vertically orientated towards the
hymenium and some continuing into it as stout, pigmented paraphyses; ascogenous hyphae
similarly pigmented, with swollen cells c. 3-5 /xm wide. Excipulum not evident, even in sections
of young apothecia.
Pycnidia usually present and numerous, immersed, black, 40-200 /xm diam; in section with a
single circular or ovate locule but often becoming internally convoluted with up to 6 locules, wall
dark green K- , HNOs-f- purple-red in upper part, turning paler below and dilute brownish or ±
hyaline at the base; conidiogenous cells irregularly subcylindrical, 5-10 x 1-2-1 -5 /xm, often with
one or two percurrent proliferations; conidia (mesoconidia) ± cylindrical or sometimes oblongobovoid,
sometimes biguttulate and often ± constricted in the middle, 3-8-6(-6-6)xl-l-7(-2)
/xm.
Chemistry: Thallus K-, C-, KC-, PD-; sections of apothecia C-; t.l.c: no substances.
Observations: Micarea sylvicola is characterized by its convex-globose, often tuberculate,
black apothecia, green or blue-green hymenium, very dark green-black or brown-black
hypothecium (appearing green, or rarely purplish, in K), and ellipsoid to ovoid, simple spores.
The variation in hypothecial pigmentation is similar to that found in such species as M.
assimilata, M. crassipes, and M. melaena. M. tuberculata is rather similar to M. sylvicola but has
generally smaller apothecia, a more shallow hymenium, narrower, oblong-ovoid spores that are
often 1-septate, and shorter conidia. Forms of M. bauschiana with greenish pigment in the
hypothecium have been confused with M. sylvicola, however the pigment is always dilute and
confined to the gel-matrix such that the hyphae appear hyaline in K (at x 1000) . The thallus of M.
sylvicola is often provided with a blue-grey tinge due to green-pigmented hyphae near the
surface; such coloration has not been noticed with the thalli of M. bauschiana and M.
tuberculata. Another species often confused with M. sylvicola is Lecidea erratica Korber, which
can be distinguished by its thinly marginate young apothecia, and distinct excipulum when
observed in section.
Habitat and distribution: M. sylvicola is mainly found on dry shaded rocks in the communities
belonging to Micareetum sylvicolae, but it sometimes occurs in periodically wetter situations on
rock faces, upper sides of boulders, and loose stones in woodlands where it may be associated
with such species as Baeomyces rufus, Cystocoleus ebeneus, Fuscidea recensa, Huilia tuberculosa,
Parmelia saxatilis, Rhizocarpon hochstetteri, R. obscuratum, R. oederi, Scoliciosporum
umbrinum, Trapelia involuta, and in one instance (Coed Hafod, Denbigh) Bacidia vezdae. In
addition, it is sometimes found on old fence posts in upland districts.
In the British Isles M. sylvicola is more confined to upland districts and is less common than M.
bauschiana. It seems to be particularly prevalent in Wales and south-east Scotland, and
curiously rare in western Scotland and Ireland. Further field-work is required to establish
whether or nor its apparent scarcity in these latter areas is real or merely an artefact resulting
from uneven recording. However, my field observations in western Scotland suggest that its
niche in the Micareetum sylvicolae is there occupied by M. lutulata. M. sylvicola is widely
distributed in Scandinavia, but rarely found from north of about latitude 67°N. Elsewhere in
Europe I have seen specimens from Germany (Hessen and Baden-Wiirttemberg), eastern
Austria, northern Italy, south-west Poland and the mountain regions of Czechoslovakia. From
outside Europe I can confirm its presence in north-eastern North America (New York and
Newfoundland).