Bulletin of the British Museum (Natural History)

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LICHEN GENUS MICAREA IN EUROPE 23 Fig. 1 Some thallus types in Micarea. A, areolate-type without cortex but with amorphous covering layer (e.g. LI lignaria). B, areolate-type without cortex or amorphous covering layer (e.g. M. denigrata). C, areolate-type with both cortex and amorphous covering layer (M. elachista). D, goniocysts (A/, prasina). Scale = 50 /Ltm. The outermost hyphae of areolae are frequently coloured or surrounded by a pigment , usually that which is found in the upper hymenium of the apothecia, or the pycnidial walls, of the given species; for example, the dilute olivaceous, K+ violet pigment in M. denigrata, M. elachista, M. globulosella, M. nitschkeana, and M. subviolascens, the green, K— , HNO3+ red pigment in M. cinerea, M. lignaria, M. peliocarpa, M. sylvicola, and M. ternaria, and the brown, K- , HNO3— pigment in M. subnigrata. The intensity of pigmentation is much dependent on exposure to light and pigment may be entirely absent in shade forms. Species that always lack pigment in their apothecia and pycnidia (e.g. M. alabastrites, M. pycnidiophora, amd M. stipitata) similarly lack pigment in the thallus. In the areolae of most species the algal layer is in direct contact with the substratum. However, a white medulla, devoid of algal cells, may be formed in the larger areolae of some species, e.g. M. incrassata, M. intrusa, M. lignaria, and M. subnigrata.
24 BRIAN JOHN COPPINS (ii) Goniocyst-type (Fig. ID) Several species have a finely granular thallus composed of discrete, ± globular structures, mostly c. 12-40 /am diam. These ecorticate granules consist of clustered algal cells intertwined and surrounded by short-celled hyphae, and are never protected by an amorphous covering layer. They are often seen to have short protruding hyphae, but they never have distinct spines as found in some species of Vezdaea (Poelt & Dobbeler, 1975). They are similar to soredia, but because they are the main component of the thallus and not derived from specialised structures (soralia) or eroding or disintegrating parts of a different thallus type (see (iii) below), the term goniocyst (Ozenda, 1963) seems the most applicable for them. In M. prasina, M. hedlundii, and M. melanobola the thallus is composed entirely of goniocysts, the first of which appear to arise directly from the prothalline hyphae; further development is presumably by a process of division or budding from existing goniocysts. M. botryoides has a 'primary' thallus of flattened granular-areolae and in a few specimens I have noticed goniocysts developing from these areolae, which then become obscured as the goniocysts proliferate. However, in most specimens of M. botryoides no areolae can be seen; either they have become obscured or, perhaps in some cases the thallus develops as goniocysts from the outset. In M. prasina and M. melanobola the outermost hyphae of superficial (exposed) goniocysts are often surrounded by the K+ violet pigment which also occurs in the upper hymenium of these species. When well developed, thalli composed of goniocysts have a ± gelatinous appearance when moist; this was the reason why Elias Fries originally placed the genus Micarea in his 'Tribus Collemaceae'. The thallus of M. synotheoides consists of small dark granular-areolae and is somewhat intermediate between the 'areolate-type'. The thallus of M. myriocarpa sometimes has a scurfy appearance but is often organized into small (10-15 /am diam) goniocyst-like granules. (iii) Sorediate-type This is represented by the apparently closely related M. leprosula and M. subleprosula. Their thalli are essentially of the 'areolate-type' but their areolae lack an amorphous covering layer and are very fragile (easily broken by touching with the point of a needle), often breaking down or eroding to form irregularly shaped, pale green or yellowish green soredial granules, c. 20-50 /Ltm diam. (iv) Smooth- or scurfy-type Included here are thalli which, although developed on the surface of the substratum, are not organized into discrete areolae or goniocysts. The thalh may be smooth, continuous to rimose, or irregularly scurfy-granular. Such thalli may be formed by species that normally have well defined areolae (e.g. M. lignaria and M. melaenida) or, by lignicolous species whose thalli are often endoxylic (e.g. M. anterior, M. nigella, and M. olivacea). The thalli of M. bauschiana and M. lutulata vary from smooth or rimose, to scurfy-granular, and lack areolae, whereas the similar M. lithinella, M. sylvicola, and M. tuberculata sometimes produce areolae. Another two species whose thalli fall within this category are M. adnata and M. turfosa. (v) Immersed-type The thallus of many lignicolous species is indistinct and developed below the surface of the substratum, which may have a bleached appearance (cf. M. muhrii). An endoxylic thallus is occasionally formed by species that more characteristically have superficial areolae, e.g. M. cinerea, M. denigrata, M. lignaria, M. muhrii, and M. peliocarpa. Conversely, M. melaeniza and M. misella are usually endoxyUc but forms with areolae are sometimes encountered. The thallus in M. anterior, M. nigella, and M. olivacea is often endoxylic, but a thin ± smooth crust is sometimes formed on the surface of the lignum. The thalli of M. contexta, M. eximia, and M. rhabdogena are invariably endoxylic. Sections of the substratum show small goniocyst-like clusters (c. 15-40 /am diam) surrounded and interconnected by pigmented hyphae. As in the relevant examples in thallus types (i-iii), and in M. turfosa in group (iv), the pigment involved is that found in the upper hymenium or pycnidial walls of the given species, viz. : dark green and K— in M. contexta and M. eximia, and olivaceous and K-f- violet in M. rhabdogena.
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76 BRIAN JOHN COPPINS Fig. 45 M. li
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78 BRIAN JOHN COPPINS B OOQog Fig.
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84 BRIAN JOHN COPPINS In the case o
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86 BRIAN JOHN COPPINS 6 - 5h 4 3 2
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. 88 BRIAN JOHN COPPINS the epithec
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90 BRIAN JOHN COPPINS fM. elachista
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92 BRIAN JOHN COPPINS Saxicolous ha
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LICHEN GENUS MICAREA IN EUROPE 95 T
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LICHEN GENUS MICAREA IN EUROPE 97 a
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Infrageneric considerations LICHEN
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5. Micarea bauschiana (Korber) V. W
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32. Micarea osloensis (Th. Fr.) Hed
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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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