Bulletin of the British Museum (Natural History)
Bulletin of the British Museum (Natural History)
Bulletin of the British Museum (Natural History)
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LICHEN GENUS MICAREA IN EUROPE 29<br />
O<strong>the</strong>r extreme those <strong>of</strong> M. contexta, M. eximia, and M. myriocarpa are ± globose from <strong>the</strong><br />
beginning and <strong>of</strong>ten tuberculate . The range <strong>of</strong> variabihty for most o<strong>the</strong>r species falls somewhere<br />
between <strong>the</strong>se last two extremes. Apo<strong>the</strong>cia are usually sessile (or partly hidden by adjoining<br />
areolae or goniocysts) but occasionally, as with M. lignaria, M. botryaides, and M. ternaria, <strong>the</strong>y<br />
may be turbinate or short-stalked (due to vertical elongation <strong>of</strong> excipular and (or) hypo<strong>the</strong>cial<br />
tissues), but only in M. crassipes and an undescribed species from New Zealand is this a constant<br />
feature (Figs 3E, 4B). Apo<strong>the</strong>cia are usually immarginate, but in those species with a well<br />
differentiated excipulum (e.g. M. cinerea, M. denigrata, M. muhrii, M. peliocarpa, and M.<br />
ternaria), a faint marginal zone is sometimes apparent, especially in young apo<strong>the</strong>cia. This zone<br />
is rarely raised above <strong>the</strong> level <strong>of</strong> <strong>the</strong> disc, but it is <strong>of</strong>ten paler in colour (especially when wet) and<br />
slightly more glossy. Even in M. crassipes, <strong>the</strong> only species whose apo<strong>the</strong>cia regularly exhibit a<br />
distinctly raised marginal rim, this feature is soon occluded as <strong>the</strong> disc expands and becomes<br />
convex.<br />
The dimensions <strong>of</strong> apo<strong>the</strong>cia in Micarea fall mainly within <strong>the</strong> range 0- 1-0-6 mm diam. In<br />
some species (e.g. M. denigrata, M. peliocarpa, and M. prasina) <strong>the</strong>re is considerable variation<br />
in apo<strong>the</strong>cial size, but in o<strong>the</strong>rs it may be less so. Characteristically small apo<strong>the</strong>cia (