. Bulletin of the British Museum (Natural History). Botany; Botany. 96 H. KROG & T. D. V. SWINSCOW. Fig. 18 Parmelia maclayana Mull. Arg., Nordal INB 849 (O). Rule = 1 cm. Thallus corticolous or saxicolous, coriaceous, pale grey. Lobes (0-5) 1-2 (2*5) cm broad, entire or crenate-dentate, ciliate, cilia sparse, 0'5-2 (3) mm long. Upper side emaculate, irregularly cracked towards the centre. Medulla white. Underside smooth or rugose, black in the centre, with a dark brown marginal zone, rhizines of medium length, in scattered groups, sometimes coming close to the margins. Soralia and isidia
. Bulletin of the British Museum (Natural History). Botany; Botany. 96 H. KROG & T. D. V. SWINSCOW. Fig. 18 Parmelia maclayana Mull. Arg., Nordal INB 849 (O). Rule = 1 cm. Thallus corticolous or saxicolous, coriaceous, pale grey. Lobes (0-5) 1-2 (2*5) cm broad, entire or crenate-dentate, ciliate, cilia sparse, 0'5-2 (3) mm long. Upper side emaculate, irregularly cracked towards the centre. Medulla white. Underside smooth or rugose, black in the centre, with a dark brown marginal zone, rhizines of medium length, in scattered groups, sometimes coming close to the margins. Soralia and isidia absent. Apothecia submarginal, stipitate, up to 3 cm in diameter, thalline exciple more or less rugose, maculate, thalline margin thin, smooth or weakly crenate, disc imperforate or with a small perforation, spores 12-15x7-10 Conidia sublageniform, 6-7 jum long. TLC: (1) alectoronic acid, unknown with alectoronic acid, atranorin; (2) alectoronic acid, tf-collatolic acid, atranorin. Parmelia maclayana has been separated from P. procera mainly by its perforate apothecia. However, this is a variable feature in P. maclayana; the only apothecium in one of the type specimens, for example, is imperforate. There is a small chemical difference between them, but it is too slight to warrant the acceptance of two different species. Parmelia breviciliata differs from P. maclayana only in being saxicolous. The broad lobes, huge apothecia, small, thin-walled spores, and sublageniform conidia are the same in all three taxa. Chemotype (2) is represented only by the type of P. procera and by the specimen Greenway 1001 cited below; the rest of the specimens belong in chemotype (1). In East Africa Parmelia maclayana has been collected in miombo woodland, artificial habitats, and well lit sites in the lower montane forest between c. 900 and 2200 m altitude. We have also seen specimens from Sierra Leone, Cameroon, Zambia, Zimbabwe and Malawi. Hale (1965, under P. breviciliata, P. procera, and P
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