LTIf'AXORA.j LKCAXO-LECIDEEl. 355 



Form dispersa Leight. Lich. Fl. ed. 3 (1879), p. 159. Thallus 

 ptilvinate, the pulvinuli more or less distantly scattered, rounded, 

 ttiinid, convex, white-suffused. Apothecia innate, minute, crowded. 



A peculiar form which at first sight seems very distinct, but is 

 connected with the type by the state already noticed. The apothecia are 

 numerous, becoming augulose from mutual pressure. 



Hab. On calcareous rocks in a maritime district. D!str. Only in 

 X. NVales and apparently very rare. B. M. : Great Orme's Head, Carnar- 

 vonshire. 



Subsp. L. albomarginata Nyl. ex Cromb. Journ. Bot. 1874, 

 p. 147. Thallus thicker, less appressed, with the radii broader, 

 subimbricate, white at the margins. Apothecia somewhat large, 

 the thalline margin thickish, inflexed or crenate, white. Lecanora 

 saxicola var. alhomaryinata, Leight. Lich. Fl. ed. 3, p. 159. Squa- 

 maria saxicola var. albomarginata Nyl. Not. Sallsk. pro F. et Fl. F. 

 Forh. xi. (1871) p. 181. 



Entitled to rank as a subspecies on account of the marked difference in 

 the characters of the thallus. In the only entire Biitish specimen seen 

 the thallus is orbicular and moderate, the apothecia being somewhat 

 crowded in the centre. 



Hab. In crusting decayed mosses on rocks and walls in upland situa- 

 tions. Distr. Local and scarce in S. and W. England. B. M. : Near 

 Lewes, Sussex ; Cheshire. 



7. L. pruinifera Nyl. Bull. Soc. Bot. Fr. t. 13 (1866) p. 368, 

 not. 2. Thallus orbicular, opaque, whitish, subfarinaceous on the 

 surface, placodioid at the circumference (CaCl + red). Apothecia 

 moderate, csesio-pminose, the thalline margin subcrenate or some- 

 times entire; spores ellipsoid, 0,010-13 mm. long, 0,005-6 mm. 

 thick; hymenial gelatine bluish, then sordidly tawny-yellow with 

 iodine. Cromb. Journ. Bot. 1882, p. 274. Lecanora pruinosa 

 Chaub. in St. Amand. Fl. Agen. (1821) p. 495 has priority, but was 

 previously applied to another species of the genus. 



Near var. j3 of the preceding species, but at once differing in the sub- 

 farinaceous thallus, the pruinose apothecia, and the chemical reaction. 

 In our only British specimen the thallus is small and the apothecia few. 



Hab. On calcareous rocks in an upland tract. Dislr. Found only 

 very sparingly in \V. England. B. M. : Cleve Hill, Somersetshire. 



Subgen. 3. PLACOPSIS Nyl. Ann. Sc. Nat. Bot. t. xv. (1862) 

 p. 376. Thallus crustaceo-adnate, more or less effigurate at the 

 circumference, cephalodiiferous, the cephalodia externally placo- 

 dioid, internally containing gonimia. Apothecia lecanorine ; thecae 

 cylindrical ; spores 8na3, oblong or ellipsoid, simple ; paraphyses 

 slender ; hymenial gelatine bluish with iodine. Spermogones with 

 simple sterigmata and arcuate or substraight spermatia. 



