390 LICHENACEI, [LEcANORA. 
b. Apothecia blackish (Pyrenodesmia Mass. Mon. Blast. p. 119 
pro parte). 
53. L. candisans Scher. Spic. (1828) p. 119.—Thallus orbicular, 
adnate, squamoso-radiose, subareolate and plane in the centre, 
plicato-lobate at the circumference, glaucous- or greyish-white, 
naked or pulverulent (K—). Apothecia small, appressed, 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. 1383; Cromb. 
Lich. Brit. p. 46; Leight. Lich. Fl. p. 176, ed. 3, p. 164. Sgqua- 
maria candicans Sm. Engl. Fl. v. p. 195. Lichen candicans Dicks. 
Crypt. fase. iii. (1793) p. 15, t. 9. f.5; With. Arr. ed. 3, iv. p.17; 
Eng. Bot. t. 1778. Lecanora epiyea Ach., Hook. FI. Scot. ii. p. 50. 
Placodium epigewm Gray, Nat. Arr. i, p. 446.—Brat. Exs.: Leight. 
n, 218, 
A very distinct species, which can be confounded with no other British 
lichen, unless perhaps with Zecidea 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. 6. Cesatii Nyl. ew Cromb. Grevillea, xviii. (1889) p. 46.— 
Thallus densely white-pruinose, the radii narrow, somewhat convex. 
Apothecia cesio-pruinose, the margin at length subobliterate.— 
Placodium Cesatii Leight. Lich. Fl. ed. 3, p. 164. Ricasolia Cesatit 
(Garov.) Mass. Mem. Lich. (1853) p. 47, t. 8. f. 46. 
Distinguished by the more pruinose thallus and apothecia, the narrower, 
more convex circumferenfial 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, 
x 
y 
54. L. chalybea Scher. Enum. (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, 
