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Bulletin of the British Museum (Natural History)

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LICHEN GENUS MICAREA IN EUROPE 109<br />

3-5 />tm. Paraphyses numerosae, ramosae et anastomosantes, c. 1-1-5 jxm latae, apicibus vix incrassatis.<br />

Hypo<strong>the</strong>cium hyalinum. Excipulum bene evolutum et manifestum praesertim in apo<strong>the</strong>ciis junioribus.<br />

Conidiomata pycnidiiformia et sporodochiiformia. Pycnidia pauca et inconspicua, ± immersa, alba, c.<br />

40-60 /xm diam, producentia conidiis cylindricis 4-5-3x 1-2-1-5 ^tm. Sporodochia plerumque numerosa et<br />

conspicua, alba, pulvinata, 20-250 jxm diam, producentia conidiis cylindricis vel oblongo-ellipsoideis<br />

6-5-9-5X 2-3-3 ^tm. Thallus et apo<strong>the</strong>cia, K— , C—<br />

, PD-; sine materia chemica.<br />

Typus: Caledonia, Argyll, Dunoon, Benmore, ad River Eachaig, ad corticem Alni, 18 xi 1977, leg. B. J.<br />

Coppins 3256 (E-holotypus).<br />

Thallus effuse, thin, ± smooth or finely scurfy-granular, pale grey-green, ra<strong>the</strong>r waxy in<br />

appearance; white, arachnoid, prothalline hyphae sometimes visible (x50). Phycobiont<br />

micareoid, cells 4-7 jxm diam.<br />

Apo<strong>the</strong>cia usually numerous but occasionally few or absent, pallid to pale straw-brown or pale<br />

reddish brown; at first ± plane, adnate, ± immarginate but <strong>of</strong>ten with a white rim, c. 30-50 /am<br />

wide, from which a few white, arachnoid hyphae are sometimes seen to arise and penetrate into<br />

<strong>the</strong> thallus; later becoming convex although remaining adnate and never becoming constricted<br />

below; dispersed, or <strong>of</strong>ten confluent, and frequently coalescing to form large, irregular, waxy,<br />

nodulose clusters; individual apo<strong>the</strong>cia 0-2-0-4(-0-6) mm diam, clusters up to 2 mm broad.<br />

Hymenium 35-40 /xm tall, hyaHne or dilute straw-yellow, K-. Asci clavate, 30-35x10-12 /xm.<br />

Spores ellipsoid, ovoid, oblong-ellipsoid, oblong-ovoid or oblong, <strong>of</strong>ten slightly constricted at<br />

<strong>the</strong> septum, (0-)l -septate, 9-16x3-5 fxm. Paraphyses numerous, branched and anastomosing,<br />

c. 1-1-5 fjLm wide and scarcely widening above; apices much branched and entangled. Hypo<strong>the</strong>cium<br />

c. 40-120 /xm tall, hyaline; hyphae hyaline, c. 1-2 ^tm wide, interwoven but becoming ±<br />

vertically orientated towards <strong>the</strong> hymenium, intermixed with short-celled ascogenous hyphae<br />

that are up to 5 /xm wide. Excipulum well developed and clearly seen in young apo<strong>the</strong>cia, c.<br />

30-35 /xm wide; hyphae radiating, branched and anastomozing, c. 1-2-5 /xm wide.<br />

Conidiomata <strong>of</strong> two types, one pycnidial, <strong>the</strong> o<strong>the</strong>r sporodochial. Pycnidia sometimes present<br />

but <strong>the</strong>n usually few in number and inconspicuous, white, immersed, c. 40-60 ^im diam;<br />

conidiogenous cells ± cylindrical, 6-10x1-1-5 /xm; conidia (mesoconidia) cylindrical, sometimes<br />

faintly biguttulate, 4—5-3xl-2-l-5 /xm. Sporodochia usually present, numerous and<br />

conspicuous, resembling small apo<strong>the</strong>cia, white or pallid, pulvinate, 80-250 /xm diam; conidiogenous<br />

cells cylindrical, 10-20x1-7-2 fxm; conidia (macroconidia) cylindrical to oblong<br />

ellipsoid or occasionally oblong-obovoid, simple, eguttulate, 6-5-9-5x2-3-3 fxm.<br />

Chemistry: Thallus and apo<strong>the</strong>cia K— , C— , PD-; no substances detected by t.l.c.<br />

Observations: Micarea adnata is easily recognised by <strong>the</strong> combination <strong>of</strong> a pale grey-green, ±<br />

waxy thallus, pale, adnate to clustered apo<strong>the</strong>cia and, above all, by <strong>the</strong> presence <strong>of</strong> sporodochia.<br />

These cushion-like conidiomata, which resemble small apo<strong>the</strong>cia, produce conidia externally<br />

over <strong>the</strong>ir surface; such structures are unknown in any o<strong>the</strong>r Micarea, and appear not to have<br />

been previously reported for lichenised fungi. The ra<strong>the</strong>r large, non-septate, oblong conidia<br />

produced by <strong>the</strong> sporodochia are probably homologous to <strong>the</strong> curved or filiform and <strong>of</strong>ten<br />

septate macroconidia <strong>of</strong> such species as M. cinerea, M. denigrata, and M. peliocarpa. Some<br />

specimens <strong>of</strong> M. adnata have a few pycnidia with typical mesoconidia, but microconidia have not<br />

yet been found.<br />

It is curious that this most distinctive species had not previously been afforded taxonomic<br />

recognition, although it was well known by Arnold who erroneously referred it to Biatorina<br />

prasiniza, a synonym <strong>of</strong> M. prasina. It is with forms <strong>of</strong> M. prasina with pallid apo<strong>the</strong>cia that M.<br />

adnata is most likely to be confused. However, <strong>the</strong> former has a non-waxy, granular thallus<br />

composed <strong>of</strong> goniocysts, apo<strong>the</strong>cia which soon become constricted below, usually smaller<br />

spores and an apparent absence <strong>of</strong> macroconidia. M. prasina is sometimes found to have<br />

pycnidia containing mesoconidia similar to those <strong>of</strong> M. adnata, but more frequently it has<br />

pycnidia containing microconidia. In addition, well developed specimens oiM. prasina have one<br />

<strong>of</strong> three distinctive substances detectable by t.l.c, whereas M. adnata contains no lichen<br />

substances. M. anterior is similar to M. adnata in being lignicolous with pale apo<strong>the</strong>cia and<br />

spores that are mainly 1-septate; however, its apo<strong>the</strong>cia are usually darker, varying from a pale

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