LECASO-LECIDEEI. 



351 



Characterized by the type of the thallus, which is comparable with 

 that of Pdrtiteliijps'is, and bv the structure of the spermogones, which are 

 immersed, their ostioles being concolorous with the thallus. 



Fig. 59. 



Lecanora (Squamaria) crassa Ach. a. A theca and paraphysis, x350. 

 b. Two spores, X 500. c. Sterigmata and spermatia, x 500. 



2. L. crassa Ach. Lich. Univ. (1810) p. 413. Thallus indeter- 

 minate or suborbicular, subcartilaginous, loosely adpressed, thick, 

 squamoso-imbricate, pale-livid or pale-yellowish ; squamules some- 

 what depressed, roundly lobato-crenate (K ). Apothecia mode- 

 rate, sessile, plane or somewhat convex, reddish-brown, the thalline 

 margin entire, at length excluded ; spores ellipsoid or oblongo-ellip- 

 soid, 0,011-14 mm. long, 0,005-6 mm. thick. Cromb. Grevillea, 

 xviii. p. 44 ; Hook. Fl. Scot. ii. p. 51. Squamaria crassa Sm. Eng. 

 Fl. v. p. 193 ; Mudd, Man. p. 127 ; Cromb. Lich. Brit. p. 44 ; 

 Leight. Lich. Fl. p. 171, ed. 3, p. 157. Psoroma crassum Gray, Nat. 

 Arr. i. p. 444. Lichen crassus Huds. Fl. AngL ed. 2 (1778), p. 530 ; 

 Eng. Bot. t. 1893. Lichen cartilagineus Lightf. Fl. Scot. ii. p. 815 ; 

 With. Arr. iv. p. 29. Lichenoides cartilagineum, scutellis fulvis 

 2)lanis Dill. Muse. 179, t. 24. f. 74. Brit. Exs. : Leight. n. 5 ; Larb. 

 Caesar, n. 73; Lich. Hb. n. 333; Cromb. n. 157; Bohl. n. 2; 

 Dicks. Hort. Sic. n. 24. 



The largest British species of the subgenus, with the thallus usually 

 very much expanded, rarely smaller and somewhat orbicular, often here 

 and there whitish. "With us it is much less variable than it is in warmer 

 regions, presenting only the following form. It is usually well fertile, the 

 apothecia becoming rather large in age. 



Hab. On the ground and on rocks, chiefly calcareous, in maritime and 

 upland districts. Distr. General and common in England and Wales ; 

 rarer in Scotland, Ireland, and the Channel Islands. B. M. : Quenvais, 

 Island of Jersey ; Islands of Herm and Guernsey. Hur^tpierpoint, 

 Sussex ; Berry Head, S. Devon ; St. Merryn, Cornwall ; Cleeve Hill and 

 Cheddar Cliffs, Somersetshire ; St. Vincent's Rocks, Bristol, Gloucester- 

 shire ; Pont Eynon, Glamorganshire ; near Tenby, Pembrokeshire ; Aber- 

 dovey, Merionethshire ; Snowdon and Great Orrne's Head, Carnarvon- 



