PIIYSCIA.] PnTSCIEI. 309 



f. 71 c, — Brit. Ex8. : Mudd, n. 83; Leight. n. 370; Cromb. n. 51 ; 

 Larl). Lich. lib. n. 48. 



W'fU characterized by the thinner, more adnate thallas, the shorter and 

 marginally sorediate laciniic, and the smaller apothecia with their usually 

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

 which are sometimes very abundant and obliterate the lacinise in the 

 centre of the thallus, make it a distinct sub-^iiecies. In our specimens 

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

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



Ha/j. On the trunks of trees, rarely on old walls, in maritime, lowland, 

 and upland cultivated tracts. — Di<lr. General and common in most parts 

 of England ; apparently rare in Scotland and the Channel Island-; ; not 

 yet with certainty gathered in Ireland. — 15. M. : Island of Guernsey. 

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

 Forest, Essex ; Basingstoke, Kent ; Glyude, .Sussex; Lymington, Hants ; 

 Ryde and Appuldurcombe, Isle of Wight ; near Cheltenham and Ciren- 

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

 Pampisford, Cambridgeshire; near Adderbury, Oxfordshire; Malvern 

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

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

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

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



Subsp. 3. P. muscigena Xyl. Syn. i. (ISGO) p. 4IS.— Ihallus do- 

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

 livid-chestnut or cervine-brown, usually eccsio-pruinose ; lacinice 

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



the thalline margin crenate ; spores 0,024-30 mm. long, 0,011-1.5 

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

 muscigena Leight. Lich. Fl. Suppl. p. 479, ed. 3, p. 13G. Parmelia 

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



Distinguished by the lacinite, 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 aot present, nor are the 

 spermogones visible. 



Hah. 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. : Cmg TuUoch, Blair Athole, Perthshu-e. 



11. P. suhdetersa Xyl. Flora, 1878, p. 344. — Thallus orbicular, 

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

 diate : lacinise somewhat short (K — ) ; medulla yellow (K-f deeper 

 yellow). Apothecia unknown. 



Well distinguished from P. pvh-eridenta var. defersa Xyl. (which ha3 

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

 P. enter oxantha Xyl., a PjTeuean plant, but differs in not being white- 

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



