Bulletin of the British Museum (Natural History)

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LICHEN GENUS MICAREA IN EUROPE 65 Fig. 35 Micarea botryoides, conidiomata: diagram showing the various means of 'stalk' formation and branching (see text for further details). Scale = 100 /xm. The pycnidia of species which consistently lack pigment in their apothecia (e.g. M. adnata, M. alabastrites, M. pycnidiophora, and M. stipitata) correspondingly lack pigment in their wall tissues. In species with coloured apothecia the pycnidial walls are usually (at least in part) coloured also. For a given species the pigment involved is usually that found in the hymenium (or epithecium) of the apothecia, but in a few cases (e.g. M. lutulata) it is the pigment found in the hypothecium which is involved. The link between apothecial and pycnidial pigmentation helps distinguish pycnidia belonging to a Micarea from any intermixed pycnidia belonging to a non-lichenized or parasitic fungus. It further helps to distinguish the pycnidia belonging to the different species of Micarea in mixed populations; for example, the stalked pycnidia of M. misella (walls oUvaceous, K+ violet) are often found intermixed with those of other species such as M. anterior (walls reddish brown, K— ) and M. melaeniza (walls dark olivaceous, K-). When a pycnidium is deeply immersed in the thallus it is often only the uppermost part around the ostiole which is coloured, and likewise, if the pycnidium is semi-immersed it is often only the upper, exposed part which is coloured. With the exception of the species that are characteristically devoid of pigment and some forms of other species in deep shade, the walls of sessile or stalked pycnidia are coloured more or less throughout. As mentioned above, the conidiomata of Micarea species are pycnidial, but there is one exception to this. M. adnata has two anamorphic states: one in which the conidia (mesoconidia) are produced internally in immersed pycnidia; and another where the conidia (macroconidia) are borne externally on cushion-like sporodochia which resemble small apothecia. This latter state could be considered to be a hyphomycetous anamorph but comparative ontogenetic studies are required to investigate the theoretical possibility that these sporodochia have evolved from pycnidial conidiomata by an exertion of the 'hymenium', and a thickening of the subtending wall-tissue to form a supporting cushion (Fig. 36). Unfortunately this hypothesis is not supported by intermediate forms in other species, although the pycnidia (with filiform or curved-hamate macroconidia) of, for example, M. cinerea and M. peliocarpa often have widely
66 BRIAN JOHN COPPINS Fig. 36 Suggested pathway for evolution of a sporodochium (D, as in M. adnata) from a pycnidium (A). The step A^B can be seen in the macroconidial conidiomata of e.g. M. cinerea and M. peliocarpa, and the mesoconidial conidiomata of e.g. M. denigrata and M. sylvicola. No structure equivalent to 'C is known from Micarea. gaping ostioles which eventually expose the 'hymenium' . The often dubious distinctions between pycnidia, acervuli, and other types of conidiomata are discussed by Nag Raj (1981). Although the sporodochial anamorph of M. adnata has unusually large, oblong-elHpsoid conidia and the longest conidiogenous cells known in the genus, there seems to be no fundamental difference in these features from those in other Micarea anamorphs, and the mode of conidiogenesis is apparently the same in all cases (see below). Conidia Vobis & Hawksworth (1981) estimate that perhaps as many as 8000 species of Uchenized fungi have conidial anamorphs, and that in most cases a given species has only one conidium type. However, it is becoming increasingly evident that a large number of lichens (especially crustose lichens) have two conidium types, although many of the examples have not yet been notified in the literature. Some examples from my own studies include Anisomeridium biforme, A. juistense, Catillaria globulosa, Lecania cyrtellina, Lecanora quercicola, and Opegrapha niveoatra. Hedlund (1895) found M. denigrata and M. prasina to each have two conidium types and during the present study 16 of the 45 European species of Micarea have been found to have two conidium types. Even more surprising has been the discovery that three species {M. denigrata, M. nitschkeana, and M. lignaria) each have three conidium types (Figs 42, 45), and to my knowledge these are the first reported instances of fungi (whether lichenized or not) with more than two pycnidial (coelomycetous) anamorphs. There are, however, a few species of sooty
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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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