PLACODIUM | PHYSIACEE 213 
20. Pl. pyraceum Anzi Anal. Lich. p. 10 (1858),—Thallus 
effuse, thin, granular-leprose or -areolate, greyish-white, with a 
whitish hypothallus, often disappearing (Kf + reddish). 
Apothecia numerous, generally very small, orange - yellow 
(K + crimson), with a thalline margin, becoming plane, with 
only the paler proper margin prominent ; paraphyses clavate, 
sometimes branched and septate at the tips, the cells thick- 
walled; spores oblong-ellipsoid, 11-16 p» long, 5-7 wp thick. 
Parmelia cerina var. pyracea Ach. Meth. Lich. p. 176 (1803). 
Lecanora pyracea Nyl. in Not. Siillsk. Faun. & Fl. Fenn. Forh. 
n. ser. v. p. 129 (1866); Cromb. Lich. Brit. p. 47 pro parte & 
Monogr. i. p. 383; Leight. Lich. Fl. p. 221; ed. 3, p. 211 
pro parte. 
Exsicc. Johns. n. 108; Leight. n. 118; Mudd n. 101. 
Allied to Pl. cerinum, but differs in the more scanty thallus and 
smaller apothecia, which scarcely show a thalline margin. It is 
constantly associated with other crustaceous species, and may seem 
to have a thallus different from its own. 
Hab. On rocks and stones, rarely (in our country) on trees in 
maritime and upland regions.—Disty. Here and there throughout the 
British Isles, probably often overlooked.—B. M. St. Merryn, Corn- 
wall; near Bovey Tracey; near Ryde, I. of Wight; Hastings, the 
South Downs and Beeding Downs, Sussex; near Cirencester, 
Gloucestershire; Barmouth, Merioneth ; near Newton, Ingleborough, 
Langbraugh and near Easby, Cleveland, Yorkshire ; Wark-on-Tyne 
and Chollerford, Northumberland; Staveley near Kendal, Westmore- 
land; Ballachulish, Argyll; Ben Lawers, Perthshire; near Fort 
William, Invernessshire; Ballynahinch, Connemara, Galway; West- 
port, Mayo. 
Form submersum A. L. Sm.—Thallus thin, dark, becoming 
coarsely areolate, otherwise resembling the species.—Lecanora 
pyracea f. submersa Nyl. in Flora Ixvui. p. 43 (1885) ; Cromb. 
Monogr. 1. p. 384. Specimen not seen. 
Hab. On stones in streams.—Distr. Found only in W. Ireland 
(near Kylemore, Connemara, Galway). 
Var. pyrithromum A. L. Sm.—Thallus paler, generally 
obsolete. Apothecia more convex, deep-yellow or rusty-red ; 
spores oblong or broadly ellipsoid, 10-13 p long, 4-10 » thick.— 
Lecidea rupestris var. pyrithroma Ach. Lich. Univ. p. 206 (1810). 
Lecanora pyracea t, pyrithroma Nyl. in Bull. Soc. Bot. Fr. xiii. 
p. 367 (1866) ; Cromb. Lich. Brit. p. 47; var. pyrithroma Cromb. 
in Grevillea xviii. p. 46 (1889) & Monogr. i. p. 384 (non Leight.). 
Kasice. Larb. Lich. Hb. n. 335 & Lich. Cantab. n, 25. 
Differs chiefly in the absence of thallus and in the shorter, some- 
times broader spores. It is generally mixed up with other lichens 
with the apothecia parasitic on their thallus. 
Hab. On rocks, walls and flints in lowland and upland regions.— 
Distr. Rare from E, and N. England, the Grampians and N.E. 
