Bulletin of the British Museum (Natural History)

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LICHEN GENUS MICAREA IN EUROPE 115 ± vertically orientated near the hymenium, c. 1-7-2-7 fxm wide, embedded in a densely pigmented matrix; ascogenous hyphae c. 1-7-2-7 /xm wide, embedded in a densely pigmented matrix; ascogenous hyphae c. 2-5-5 fxm wide. Excipulum reflexed, mottled reddish brown or sordid olivaceous; hyphae radiating, branched and anastomosing, 1-5-2 /xm wide. Pycnidia rare, semi-immersed to sessile, black, 40-100 /^m diam; walls dull reddish brown, or dull olivaceous in part; conidia (? microconidia) cylindrical, 6-9x1-1-5 /xm. Chemistry: Thallus K— , C— , KC— , PD — ; t.l.c: no substances. Observations: Micarea assimilata is characterized by its conspicuous, whitish, verrucose areolae which are often intermixed with brown cephalodia, rather large, convex, black apothecia, green (K— ) epithecium, dark purple-brown hypothecium and predominantly simple, large spores. It is apparently closely related to M. crassipes, M. incrassata, M. melaenida, and M. subviolascens , all of which share rather stout, simple or sparingly branched paraphyses, rather stout excipular hyphae, dark hypothecia and an absence of lichen substances. In many ways M. assimilata is identical to M. incrassata and both occur in similar habitats; indeed the latter has often been considered a variety (var. infuscata) of the former (e.g. Anderson, 1964; Hertel, 1977). However, M. incrassata differs in several respects, the most important of which is its quite different, red-brown hypothecium which lacks any trace of purple pigmentation in water, K or HNO3. In addition, it has an often darker thallus, less prominent apothecia and a generally higher proportion of septate spores. M. subviolascens is similar in appearance to M. assimilata, but grows on rock and has a green, K-l- violet epithecial pigment. M. melaenida differs from the last three species in its comparatively small apothecia and less conspicuous thallus, absence of green pigmentation in apothecial tissues, preponderance of 1-septate spores, shorter conidia, and confinement to argillaceous, or fine-grained, mineral soils. M. crassipes occurs in much the same habitats as M. assimilata and the two species have been much confused. However, M. crassipes is easily distinguished by its apothecia which are thinly marginate (at least when young) and markedly constricted below, often being turbinate or even short-stipitate; also by its thallus which is composed of small granular-areolae which sometimes proliferate to give it an isidiose appearance. In section, the apothecia of M. crassipes display a well-developed excipulum and a distinctly two-zoned hypothecium. Pycnidia are rare and difficult to find in members of the M. assimilata group, and have not yet been found at all in M. subviolascens. The remaining species appear to have one conidium type only; although the conidia are rather large, they afe probably microconidia. However, the relatively shorter and broader conidia of M. crassipes may be better described as mesoconidia. Cephalodia are here reported from M. assimilata and M. incrassata, apparently for the first time. In both cases the blue-green alga concerned is Nostoc, which loses its filamentous form. In addition, irregular clusters of partially disrupted Stigonema filaments are sometimes present amongst the areolae of M. assimilata, M. incrassata, and also M. subviolascens. Hyphae, presumably belonging to the lichens, are seen to ramify through these clusters; but whether or not these loosely organised structures can be considered to be cephalodia is a problem requiring further detailed anatomical and experimental investigation. Cephalodia or cephalodia-like structures have not been encountered in any other Micarea species. The closely related Lecidea limosa Ach. and L. stenotera (Nyl.) Nyl. have often been confused with M. assimilata and M. incrassata, but they can be distinguished by their pale hypothecia, paraphyses which are individually supplied with a dense, hyaline, gelatinous sheath, and more organised excipular structure. Together with Catillaria contristans (Nyl.) Zahlbr. they probably represent a distinct genus within the Lecideaceae, although perhaps not far removed from Micarea. In British herbaria (at least) there has been much confusion between M. assimilata and Lecidea hypnorum Lib. The latter has marginate, brown-black apothecia, simple paraphyses, 0(-3)-septate spores which become straw coloured and finely warted with age, a reddish brown excipulum composed of radiating, stout, pachydermatous, heavily conglutinated hyphae, c. 3-5 /xm wide, and bears little resemblance to a Micarea. In addition, the hymenium, hypothecium and excipulum of L. hypnorum (and the related L. berengeriana (Massal.) Th. Fr. , and L. sanguineoatra auct.) often contain minute granules of a dark violet (K-l- aeruginose) pigment.
116 BRIAN JOHN COPPINS More understandable cases of mistaken identity involve Lecidea caesioatra Schaerer, which bears a close superficial likeness to M. incrassata. It can be distinguished from this Micarea by its dark blue-grey apothecia which have a caesious bloom when wet, excipulum of conglutinated (in K) hyphae, and non-micareoid phycobiont with cells c. 8-12 /xm diam. Habitat and distribution: M. assimilata grows on decaying bryophytes and plant detritus on the ground or on soil accumulation in rock crevices in arctic (i.e. low altitudes at high latitudes) or montane situations. The realisation that this species belongs in Micarea came so late in the present study, that I have been able to examine only a limited amount of herbarium material. To date, I can confirm its presence in northern Scandinavia and the single outlying locality in Scotland. Specimens purporting to be Lecidea assimilata from the Alps and other central European mountains have proved to be M. crassipes, M. incrassata, or 'Lecidea' species not referable to Micarea. Material of 'Lecidea assimilata'' from Greenland distributed as Hansen Lich. Greenland Exs. Ill and 247 belongs to Lecidea stenotera and L. limosa respectively. The Scottish locality is Ben Lawers in Perthshire, a mountain long renowned for its arctic-alpine flora (Anon, 1972; James, 19656). M. assimilata was collected there by W. L. Lindsay in 1856. Recent collections from Ben Lawers, and other Scottish localities, are referable to other species, such as Lecidea caesioatra, L. hypnorum, L. limosa, and Micarea incrassata. Exsiccata: Krypt. Exs. Vindob. 2268 (BM, H). Malme Lich. Suec. 216 (H). Map 3 Micarea assimilata ® Before 1950 + Micarea incrassata # 1950 onwards
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20 BRIAN JOHN COPPINS Micarea The g
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22 BRIAN JOHN COPPINS Morphology Th
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24 BRIAN JOHN COPPINS (ii) Goniocys
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36 BRIAN JOHN COPPINS Fig. 10 A, M.
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38 BRIAN JOHN COPPINS Fig. 12 A,M.
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40 BRIAN JOHN COPPINS r\ U Fig. 14
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44 BRIAN JOHN COPPINS Fig. 18 M. le
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46 BRIAN JOHN COPPINS Fig. 20 A-B,
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48 BRIAN JOHN COPPINS Fig. 22 M. me
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50 BRIAN JOHN COPPINS Fig. 24 A, M.
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52 BRIAN JOHN COPPINS Fig. 26 M. pr
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54 BRIAN JOHN COPPINS VJ Fig. 28 A,
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56 BRIAN JOHN COPPINS Fig. 30 M. su
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58 BRIAN JOHN COPPINS Fig. 31 - con
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60 BRIAN JOHN COPPINS Fig. 33 M. tu
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LICHEN GENUS MICAREA IN EUROPE 165
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34. Micarea prasina Fr. LICHEN GENU
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conferanda (Lecidea) 205 confusula
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populina (Lecidea, Micarea) 31,32 p
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