PUYSCIA.] PHYSCIEI. 321 



i. p. 439. Sqnamaria elirlna Sm. Eng. Fl. v. p. 197. Lichen 

 elceinus Eng. Hot. t. 21o8.-Jlrit. Exs. : Cromb. n. 152 ; Larb. Lich. 

 Hb. n. 49. 



The thallus is often leproso-pulverulent in the centre, and sometimes 

 subtffuse, through the confluence of several plants. P'roin states of P. 

 obscura, of which it has frequently been considered as a variety, it at 

 once differs in the form of the spcrmatia. The apothecia are chiefly 

 central. The sperm ogones, which are not uncommon, are olive-brown, 

 with spermatia long, acicular, about 0,018 mm. long, searcely 0,001 min. 

 thick. 



Hub. On the trunks of trees, rarely on walls, in maritime and lowland 

 districts. Distr. Probably not uncommon throughout England and W. 

 Ireland ; rare in the Channel Islands ; apparently absent from Scotland. 

 B. M. : Noirinont, Island of Jersey. Norwich, Norfolk ; Walthamstow, 

 Essex ; Glynde, Hurstpierpoint, and between Heufield and Brighton, 

 Sussex ; Lymington, Hants ; Penzance, Cornwall ; near Cirencester, 

 Gloucestershire ; Gamlingay, Cambridgeshire ; Cleveland, Yorkshire ; 

 Kendal, Westmoreland. Killarney, co. Kerry ; Kylemore, co. Galway. 



Form sorediata Nyl. ex Leight. Licb. Fl. ed. 3 (1879) p. 138. 

 Thallus leproso-sorediate almost throughout, glaucous- white : lacinioe 

 more dilated at the circumi'erence and there only esorediate. Apo- 

 thecia not seen. Brit. Exs. : Larb. Lich. Hb. n. 127. 



Apart from the paler colour and the broader lacinise this differs only 

 in the much more sorediate thallus, in which respect it resembles var. 

 sitboirella Nyl. (Pyr. Or. p. 03), which does not occur in our Islands. 

 The specimens seen are sterile. 



Hab. On \valls and trees in upland districts. Distr. Only sparingly in 

 N.W. Ireland. B. M. : Letterfrack and Letter Hill, Conuemara, co. 

 Galwav. 



Tribe XVII. GYROPHOREI Nyl. Mem. Soc. Cherb. 

 iii. (1855) p. 175; Lich. Scaud. p. 112. 



Thallus membranaceo-foliaceous, monophyllous or subpolyphyllous, 

 peltate, umbilicately affixed in the centre to the substratum, cor- 

 ticate on both surfaces ; internally with white lax filamentose 

 medulla ; gonidial layer containing gonidia. Apothecia either leca- 

 noroid, or lecideine and gyrose, black ; spores solitary or usually 

 8nae, oblong or ellipsoid, simple or murali-divided, colourless or 

 brown ; paraphyses discrete. Spermogones either immersed or 

 somewhat prominent, with jointed sterigmata. 



The systematic position of this tribe has been variously regarded by 

 authors. There is no doubt, however, that this is its true place as indi- 

 cated by the character of the vegetative and reproductive organs, though 

 the structure and form of the apothecia are rather peculiar. It is a very 

 natural t*ibe, comprising two genera, the distinctive characters of which 

 have recently been definitely pointed out by Nylander. The species are 

 all saxicolous, characteristic of cold regions, and for the most part very 

 brittle when dry. 



