PHYSCIA.] PHYSCIEI. 309 



f. 71 c.Brit. Exs. : Mudd, n. 83 ; Lcight. n. 370 ; Cromb. n. 51 ; 

 Larb. Lich. Hb. n. 48. 



Well characterized by the thinner, more adnate thallus, the shorter and 

 marginally sorediate laciniae, and the smaller apothecia with their usually 

 sorediate thalline margin. These characters, more especially the soredia, 

 which are sometimes very abundant and obliterate the lacihise in the 

 centre of the thallus, make it a distinct subspecies. In our specimens 

 the apothecia, which are central, are not often present ; and the spermo- 

 gones, which are similar to those of the type, are also but rarely seen. 



Ifab. On the trunks of trees, rarely on old walls, in maritime, lowland, 

 and upland cultivated tracts. Distr. General and common in most parts 

 of England ; apparently rare in Scotland and the Channel Islands ; not 

 yet with certainty gathered in Ireland. 13. M. : Island of Guernsey. 

 Sahani Wood, Norfolk ; near Bury, Suffolk ; High Beech, Epping 

 Eorest, Essex ; Basingstoke, Kent ; Glynde, Sussex ; Lymington, Hants ; 

 Hyde and Appuldurcombe, Isle of Wight ; near Cheltenham and Cireu- 

 cester, Gloucestershire ; Edgeware, Middlesex ; near Elstree, Herts ; 

 Pampisford, Cambridgeshire; near Adderbury, Oxfordshire; Malvern 

 and near Kempsey, Worcestershire; Harboro' Magna, Warwickshire; 

 Ludlow Park, Shropshire; Aberdovey, N. Wales; Carlton, Cleveland, 

 Yorkshire ; Winderuiere, Westmoreland. Appin, Argyleshire ; Blair- 

 drummond, near Stirling ; Glen Ample, Perthshire ; Drum, near Aberdeen. 



Subsp. 3. P. muscigena Nyl. Syn. i. (1860) p. 418. Thallus de- 

 pressed at the circumference, more or less ascending in the centre, 

 livid-chestnut or cervine-brown, usually ceesio-pruinose ; laciniae 

 somewhat short, dilated and discrete (K~, CaCl~). Apothecia with 

 the thalline margin crenate ; spores 0,024-30 mm. long, 0,011-15 

 mm. thick. Cromb. Grevillea, xv. p. 78. Physcia pulverulenta var. 

 muscigena Leight. Lich. Fl. Suppl. p. 479, ed. 3, p. 136. Parmelia 

 muscigena Ach. Lich. Univ. (1810) p. 472. 



Distinguished by the lacinire, the crenate margin of the apothecia, the 

 smaller spores, and the nature of the habitat. These differences, however, 

 are scarcely sufficient to warrant our regarding it, with some older and 

 more recent authors, as a distinct species, but only as a well-marked sub- 

 species of this very variable plant. In the only British specimen gathered 

 the apothecia, which are elsewhere very rare, are not present, nor are the 

 spermogones visible. 



Hab. On decayed mosses on the ground in a subalpine region. Distr. 

 Found only on the summit of one of the Central Grampians, Scotland. 

 B. M. : Craig Tulloch, Blair Athole, Perthshire. 



11. P. subdetersa Nyl. Flora, 1878, p. 344. Thallus orbicular, 

 moderate, pale-cervine, subnaked or here and there yellowish-sore- 

 diate ; laciniaj somewhat short (K ) ; medulla yellow (K + deeper 

 yellow). Apothecia unknown. 



Well distinguished from P. prtlveruknta var. detersa Nyl. (which has 

 not occurred with us) by the colour of the medulla. It approaches 

 P. enteroxantha Nyl., a Pyrenean plant, but differs in not being white- 

 pruinose and in the medullary reaction. It is never seen fertile. 



