390 LICHEIfACEI. [lECANOEA. 



b. Apothecia blackish {Pyrcnodesmla Mass. Mon, Blast, p. 119 

 pro parte). 



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

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

 plicato-lobate at the circumfei'ence, glaucous- or greyish-white, 

 naked or pulverulent (K — ). Apothecia small, appressed, plane or 

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

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

 tate, 0,007-14 mm. long, 0,00-4-7 mm. thick. — Cromb. GreviUea, 

 xviii. p. 46. — Placodiiim candicans Mudd, Man. p. 133 ; Cromb. 

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

 rnaria candicans Sra. Engl. Fl. v. p. 105. LicJicn candicans Dicks. 

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

 Eng. Bot. t. 1778. Lecanora e_pi(jea Ach., Hook. Fl. Scot. ii. p. 50. 

 Placodium ejiigeum Graj', Xat. Arr. i. p. 446. — Brit. Exs. : Leight. 

 n. 218. 



A vei'v distinct species, which can be confounded with no otlier Biitish 

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

 which it is at ouce 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 creuate at the circumference, and 

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

 beiug chietl}' central and somewhat scattered. 



Hah. On calcareous and cretaceous rocks in maritime and upland 

 tracts. — Distr. Here and there throughout England ; vei*y rare in N. 

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

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

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

 Worcestershire ; Buxton and near Cromford, Derbyshire. Near Oswestry 

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

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

 moreland. Near Shean Ferry, Argyleshu'e. 



Yar. ft. Cesatii Nj-l. ex Cromb. Grevillea, xviii. (1889) p. 46. — 

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

 Apothecia csesio-pruiuose, the margin at length subobliterate. — 

 Placodium Cesatii Leight. Lich. Fl. ed. 3, j). 164, Hicasolia Cesatii 

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



Distinguished b}' 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. chalybsea Schaer. Enum. (1850) p. 60. — Thallus orbicular, 

 adnate, smooth, diHracto-areolate in the centre, radioso-difFract and 

 subefligurate at the circumference, wliitish- or greyish lead-coloured 

 (K + palc 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. 



