220 LICHENACEI. [PLATYSMA. 



Well distinguished from Cetraria by the form of the spermogones, 

 though in one section the form of the sperrnatia indicates some affinity. 

 The thallus is at length free, or affixed to the substratum by a lew rhiziuae, 

 and is more variable in colour than in Cetraria. When it is membrana- 

 ceo-dilated, as it sometimes is, it resembles Parmelia, but is separated 

 by the spermogones. 



A. Spermatia slightly incrassate or clavate at the obtuse apices. 



a. Thallus erect, becoming free, concolorous on both sides, 

 the laciniae elongate. 



1. P. nivale Nyl. Act. Soc. Linn. Bord. ser. 3, i. (1867) p. 295. 

 Thallus fruticuloso-erect, foliaceo-expanded, sinuato-laciniate, pale 

 straw-coloured or ochroleucous, usually tinged browri-ochraceous at 

 the base ; laciniae canaliculato-patulous, reticulato-lacunose, dentate 



at the apices (K~, CaCl~). Apothecia aclnate on the front of 



the laciniae, subterminal, moderate, yellowish flesh-coloured, the 

 margin crenulate : spores small, 0,007-9 mm. long, 0,004-5 mm. 

 thick. Nyl. Syn. i. p. 302, t. 8. f. 33 ; Cromb. Lich. Brit. p. 26; 

 Leight. Lich. Fl. p. 99, ed. 3, p. 93. Cetraria nivalis Gray, Nat. 

 Arr. i. p. 433; Hook. Fl. Scot. ii. p. 57 ; Sin. Eng. Fl. v. p. 221 ; 

 Mudd, Man. p. 78. Lichen nivalis Linn. Sp. PI. (1753) p. 1145 ; 

 Dicks. Crypt, fasc. iii. p. 17 ; With. Arr. ed. 3, iv. p. 60; Eng. Bot. 

 t. 1994. Lichenoides Idcunosum candidum ylabrum, endivice crispw 

 facie Dill. Muse. 162, t. 21. f. 56 A. Brit. Exs. : Leight. n. 43 ; 

 Mudd, n. 53 ; Cromb. n. 24. 



This beautiful species, so characteristic of Arctic and Alpine regions, 

 often forms dense tufts, occasionally of considerable size. The apothecia 

 do not occur in this country, but the spermogones are occasionally seen. 

 They appear as black marginal papillae, with sterigmata subsimple, or 

 2-3-articulate, and spermatia 0,000-7 mm. long, 0,001 mm. thick. 



Hab. On the ground among mosses and on bare detritus in alpine places. 

 Distr. Kather local, though plentiful among the Grampians, Scotland, 

 chiefly in Braemar. B. M. : Ben Lawers, Perthshire ; Bassies, Clova, 

 Forfarshire ; Lochnagar, Ben-uaboord, Morrone, Ben Avon, Ben Macdhui, 

 Cairngorm, Cairntoul, sources of the Dee, Braemar, Aberdeenshire ; Ben 

 Nevis, Inverness-shire. 



2. P. cucullatum Nyl. Act. Soc. Linn. Bord. ser. 3, i. (1867) 

 p. 295. Thallus fruticuloso-erect, foliaceo-complanate, smooth, 

 canaliculate- laciniate, pale ochroleucous, usually tinged purplish at 

 the base ; laciniae sinuato-divided, the margins connivent, undulate, 

 naked, somewhat recurved at the apices (K~, CaCl~). Apothecia 

 adnate on the back of the lobes, subterminal, often dilated, pale 

 flesh-coloured, the margin thin, or at length excluded ; spores 

 0,007-10 mm. long, 0,004 mm. thick. Cromb. Journ. Bot. 1870, 

 p. 96; Leight. Lich. Fl. p. 99, ed. 3, p. 94. Cetraria cucullata 

 Mudd, Man. p. 87. Lichen cucullatus Bellard, Obs. Bot. (1788) 

 p. 54. Lichenoides maryinibus coeuntibus et velut tubulosum Dill. 

 Muse. 162, t. 21. f. 56 n.Brit. Exs. : Cromb. n. 132. 



In Great Britain this occurs only in small, scattered tufts. It differs 



