PLACODIUM] PHYSIACEE 219 
Hab. On smooth bark.— Distr. Rare in S.E. and W. England.— 
Bb. M. Usham, Torquay; Cherry Hinton and Bottisham, Cambridge- 
shire ; near Worcester. 
30. Pl. cesiorufum A. L. Sm.—Thallus crustaceous, thickish, 
cracked-areolate, light- or dark-grey (Kf + purplish). Apothecia 
moderate in size, often crowded, becoming plane, rusty-red (K + 
purple), the proper margin prominent, lighter-coloured, often 
tflexuose and subcrenulate; paraphyses rather stout and the 
hypothecium dense, with a layer of gonidia beneath ; spores 
ellipsoid, 14-17 » long, 7-9 pw thick.—Lichen cesiorufus Ach. 
Lich. Suec. Prodr. p. 45 (1798). Lecidea cesiorufa Ach. Meth. 
Lich. p. 71 (1803) ; S. F. Gray Nat. Arr. i. p. 478(?).  Lecanora 
cxesiorufa Ny]. in Flora Ixiii. p. 388 (1880); Cromb. in Journ. 
Bot. xx. p. 273 (1882) & Monogr. i. p. 378. 
Exsicc. Johns. n. 323 (as var. grandis). 
Somewhat similar to Pl. ferrugineun in appearance, but differing 
in the structure of the hypothecium, which is of small-celled some- 
what obscure plectenchyma and with an underlayer of gonidia. The 
thallus is generally rather thick and dark-coloured. 
Hab. On siliceous rocks in maritime and inland districts.—Distr. 
Rare throughout the British Isles, perhaps not often identified. 
B. M. La Moye, Jersey; Chateau Point, Sark; The Lizard, Corn- 
wall; near Malvern, Worcestershire ; Chollerford, Northumberland ; 
St. Bees and near Penrith, Cumberland; Ayton, Cleveland, York- 
shire; Renwick, Kirkcudbrightshire ; near Edinburgh; I. of Lismore, 
Argyll; Kilkee, Clare; Achill Island, Mayo. 
31. Pl. fuscoatrum A. L. Sm.—Thallus effuse, blackish, 
cracked-areolate (K+ purple). Apothecia very small, dark rusty- 
red, with a distinct entire thalline margin ; paraphyses slender, 
branched, septate and capitate at the tips; spores ellipsoid, 
12-15 » long, 6-9 p thick.—Biatora ferruginea var. fuscoatra 
Bayrh. Uebers. p. 82 (1849). Lecanora ferruginea var. fuscoatra 
Cromb. Lich. Brit. p. 47 (1870); Leight. Lich. Fl. p. 220; ed. 3, 
p. 209. L. fuscoatra Nyl. in Bull. Soc. Linn. Norm. sér. 2, vi. 
p. 260 (1872); Cromb. Monogr. i. p. 377. 
A rare lichen, but well distinguished by the dark thallus and the 
structure of the apotheciuin. 
Hab. On schistose rocks—Distr. Rare in N.W. England, S.W. 
Highlands and N.E. Scotland.—-B. M. North of Douglas, I. of Man; 
Barcaldine, Argy)l. 
32. Pl. concilians A. L. Sm.—Thallus subeffuse, thickish, 
coarsely areolate, dark-grey or blackish (K —). Apothecia 
moderate in size, with a thalline margin, becoming plane or 
convex, and the margin disappearing, brownish black when dry, 
dark rusty-red when moist (K + dark-purplish) ; paraphyses 
branched and septate at the tips, forming a dense epithecium ; 
spores ellipsoid, 12-17 yp long, 6—9 » thick.—Lecanora ferruginea 
