390 LTCHENACEI. [LECANORA. 



b. Apothecia blackish (Pyrenodesmia Mass. MOD. Blast, p. 119 

 pro parte). 



53. L. candicans Schaer. Spic. (1828) p. 119. Thallus orbicular, 

 adnate, squamoso-radiose, subareolate and plane in the centre, 

 plicato-lobate at the circumference, glaucous- or greyish-wbite, 

 naked or pulverulent (K ). Apothecia small, oppressed, plane or 

 slightly convex, brownish-black, more or less pruinose (K ) ; the 

 thalline margin thickish, entire, persistent ; spores ellipsoid, 1 -sep- 

 tate, 0,007-14 mm. long, 0,004-7 mm. thick. Cromb. Grevillea, 

 xviii. p. 46. Placodium candicans Mudd, Man. p. 133 ; Cromb. 

 Lich. Brit. p. 46 ; Leight. Lich. Fl. p. 176, ed. 3, p. 164. Squa- 

 maria candicans Sm. Engl. Fl. v. p. 195. Lichen candicans Dicks. 

 Crypt, fasc. iii. (1793) p. 15, t. 9. f. 5 ; With. Arr. ed. 3, iv. p. 17 ; 

 Eng. Bot. t. 1778. Lecanora epiyea Ach., Hook. Fl. Scot. ii. p. 50. 

 Placodium epigeum Gray, Nat. Arr. i. p. 446. Brit. Exs. : Leight. 

 n. 218. 



A very distinct species, -which can be confounded with no other British 

 lichen, unless perhaps with Lecidea canescens (Dicks.), saxicolous, from 

 which it is at once distinguished by the type of the apothecia and the 

 absence of any thalline reaction. The thallus is small or submoderate, 

 with the radii roundly dilated and crenate at the circumference, and 

 without any visible hypothallus. It is usually well fertile, the apothecia 

 being chiefly central and somewhat scattered. 



Hab. On calcareous and cretaceous rocks in maritime and upland 

 tracts. Distr. Here and there throughout England ; very rare in N. 

 Wales and the S.W. Highlands of Scotland; not seen from Ireland. 

 B. M. : Near Beachy Head, Sussex ; Portland Island and Swanage, Dor- 

 setshire ; Cleeve Hill and Bathampton Downs, Somersetshire ; Malvern, 

 Worcestershire ; Buxton and near Cromford, Derbyshire. Near Oswestry 

 and Llanymynech Hill, Shropshire ; Great Orme's Head, Carnarvonshire ; 

 Teesdale and Eglestone, Durham ; Arnbarrow and Helsington, West- 

 moreland. Near Shean Ferry, Argyleshire. 



Var. ft. Cesatii Nyl. ex Cromb. Grevillea, xviii. (1889) p. 46. 

 Thallus densely white-pruinose, the radii narrow, somewhat convex. 

 Apothecia caesio-pruinose, the margin at length subobliterate. 

 Placodium Cesatii Leight. Lich. Fl. ed. 3, p. 164. Ricasolia Cesatii 

 (Garov.) Mass. Mem. Lich. (1853) p. 47, t. 8. f. 46. 



Distinguished by the more pruinose thallus and apothecia, the narrower, 

 more convex circumferential radii, which are also somewhat incurved at 

 the apices. The only British specimen seen is well fertile. 



Hab. On calcareous rocks in an upland district. Distr. Only very 

 sparingly in W. England. B. M. : Sherborne, Gloucestershire. 



54. L. chalybaea Schser. Eiram. (1850) p. 60. Thallus orbicular, 

 adnate, smooth, diffracto-areolate in the centre, radioso-diffract and 

 subeffigurate at the circumference, whitish- or greyish lead-coloured 

 (K + pale violet), usually limited by a blackish hypothallus. Apo- 

 thecia small, innate or immersed, plane, black, naked or pruinose 

 (K ); the thalline margin thin, entire, depressed; spores ellipsoid, 



