220 LICHENACEI. [pLATYSilA. 



"Well distiuguislied fruui Cetraria by the form of the spermoo:ones, 

 tliougli in one section the form of the spermatia indicates some atlinity. 

 The thallus is at length free, or athxed to the substratum by a tew rhiziuce, 

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

 ceo-dilated, as it sometimes is, it resembles rarmelia, 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 Xyl. Act. Soc. Linn. Bord. ser. 3, i. (1867) p. 295. — 

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

 straw-coloui'ed or ochruleucous, usually tinged brown-ochraceous at 

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



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



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

 margin crenulate : s])ores small, 0,007-9 mm. long, 0,004—5 mm. 

 thick.— ^'yl. 8yn. i. p. ;^02, t. 8. f. 33 ; Cromb. Lich. Brit. p. 26; 

 Leight. Lich. Fl. p. 99, ed. 3, p. 93. — Cetraria nivalis Gray, I^at. 

 Arr. i. p. 433 ; Hook. Fl. Scot. ii. p. 57 ; Sni. 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 hicunosum candidum glabrian, endivice crisptr, 

 /rtc?> Dill. Muse. 102, t. 21. f. 5QA.—Brit.L\vs.: 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 papilla3, with sterigmata subsimple, or 

 2-3-articulate, and spermatia 0,006-7 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, 

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

 Nevis, Inverness-shire. 



2. P. cucullatum Xyl. Act. Soc. Linn. Bord. scr. 3, i. (1867) 

 p. 295. — Thallus fruticuloso-erect, lbliaceo-com]danate, smooth, 

 canaliculato-laciniate, pale ochroleucous, usually tinged purplish at 

 the base ; laciniae siuuato-divided, the margins connivcnt, 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 cucidlata 

 :Nrudd, Man. p. 87. Lichen ciicuUatus Bollard, Obs. Bot. (1788) 

 p. 54. Lichenoides marcjinihvs coihintibus et velut tnbidosiim Dill. 

 Muse. 162, t. 21. f. 56 w.—Brit. Exs.: Cromb. u. 132. 



In (ireat Britain this occurs only iu small, scattered tufts. It differs 



