316 LICHENACEI. [PHTSCIA. 



Hob. On the smooth bark of a young tree in a maritime district. 

 Distr, Extremely local and rare, in S.England. B. M. : Near Hyde. 

 Isle of Wight. 



18. P. erosa Leight. Lich. Fl. (1871) p. 152. Thallus subor- 

 bicular, moderate, shortly laciniate, greyish or glaucous-white ; 

 beneath whitish, sparingly fibrilloso-rhizinose ; Iacinia3 crowdedly 

 imbricate, more or less ascending, rounded and eroso-lacerate or at 

 length pulverulent at the apices (K+yellow, CaCl+yellow). Apo- 

 thecia moderate, brownish-black, the thalline margin subentire ; 

 spores oblong, 0,014-20 mm. long, 0,007-10 mm. thick. Cromb. 

 Journ. Bot. 1872, p. 358 ; Leight. Lich. Fl. ed. 3, p. 139. Par- 

 melia erosa Borr. Eng. Bot. Suppl. 1837, t. 2807. Son-era ccesia 

 y. albinea (non Ach.) Mudd, Man. p. 108, t. ii. f. 31; Cromb. 

 Lich. Brit. p. 39. Squamaria tribacia Sm. Eng. Fl. ii. p. 194 pro 

 parte. Brit. Exs. : Leight. n. 266; Larb. Caesar, n. 24; Lich. Hb. 

 n. 294. 



A well-marked species somewhat resembling P. tribacia, from which 

 it is well distinguished by the efarinose and esorediate thallus, the apices 

 of the laciniee, and the different chemical reactions. The apothecia, 

 which with us are extremely rare, are chiefly central, numerous, with the 

 thalline margin at length subcrenate. 



flab. On trees, walls, and rocks in maritime and upland districts. 

 Distr. Not very general nor common throughout England and in the 

 Channel Islands ; rare in S. Scotland, the S.W. Highlands and S. Gram- 

 pians ; not yet seen in Ireland. B. M. : Rozel, St. Ouen's, and La Moyp, 

 Island of Jersey ; Jerbourg and Moulin Huet, Island of Guernsey. Bex- 

 hill and Hurstpierpoint, Sussex ; Porchester, Hants ; Plymouth and 

 Wembury, S. Devon ; near Penzance and Withiel, Cornwall ; St. Mary's, 

 Scilly ; near Swindon, Wilts ; Malvern, Worcestershire ; Nannau, Dol- 



a, Barmouth, and Aberdovey, Merionethshire ; near Ayton, Cleve- 

 , Yorkshire ; near Staveley, Westmoreland. New Galloway, Kirk- 

 cudbrightshire ; Barcaldine, Argyleshire ; Ben Lawers, Perthshire. 



19. P. astroidea Nyl. Act. Soc. Linn. Bord. ser. 3, i. (1856) 

 p. 308. Thallus orbicular, thin, closely adpressed, granulose or 

 leprose in the centre, laciniato-effigurate at the circumference, 

 greyish-white ; beneath whitish, black fibrilloso-rhizinose ; lacinia? 

 narrow, contiguous (K ^yellow, CaCl+ yellow). Apothecia innato- 

 sessile, small, concave or plane, brownish-blackish, naked or prui- 

 nose, the thalline margin inflexed, crenulate ; spores ellipsoideo- 

 oblong, 0,017-26 mm. long, 0,008-11 mm. thick. Cromb. Lich. 

 Brit. p. 39; Leight. Lich. Fl. p. 153, ed. 3, p. 139. Borrera 

 astroidea et /3. dementi Mudd, Man. p. 108, t. ii. f. 32. Parmelia 

 astroidea Clem. Ens. Add. (3807) p. 302. Squamaria dementi 

 Sm. Eng. Fl. v. p. 196. Parmelia Clementi Turn. Trans. Linn. Soc. 

 ix. p. 146, t. 13. f. 1 ; Gray, Nat. Arr. i. p. 439 ; Tayl. in Mack. 

 Fl. Hib. ii. p. 147. Lichen Clementi Eng. Bot. t. 1779. Parmelia 



