LECANORA. | LECANO-LECIDEEL. 359 
11. L. murorum Ach. Lich. Univ. (1810) p. 443; Nyl. Flora, 
1883, p. 106.—Thallus orbicular, closely adnate, usually whitish- 
suffused, subrimoso-areolate in the centre, plicato-radiose at the 
circumference, vitelline-yellow or citrine; radii somewhat turgid, 
crenate and often also inciso-plicate at the apices (K + purplish). 
Apothecia moderate, plane or convex, tawny-yellow, orange- 
coloured or concolorous with the thallus (K + purplish); the 
thalline margin entire, paler or concolorous; spores 0,009-15 mm. 
long, 0,004-7 mm. thick.—Cromb. Grevillea, xviii. p. 44; Hook. 
Fl. Scot. ii. p. 50 pro parte; Tayl. in Mack. Fl. Hib. ii. p. 140 
pro parte.—Plucodium murorum Leight. Lich. Fl. p. 175 pro parte, 
ed. 3, p. 161 pro parte ; Cromb. Lich. Brit. p. 45 pro parte ; Mudd, 
Man. p. 182 pro parte; Gray, Nat. Arr. i. p. 447 pro parte. Squa- 
maria murorum Sm. Eng. Fl. v. p. 194 pro parte. Lichen murorum 
Hoffm. Enum. (1784) p. 63; Eng. Bot. t. 2157 (lower fig.). Lichen 
Slavescens Huds. Fl. Angl. p. 445 pro parte. 
A species until recently little understood and very imperfectly limited, 
so that the trivial name of murorum, as applied to it by British and other 
authors, is, to a great extent, a nomen vagum. It appears under two con- 
ditions of growth—a larger, with the thallus more developed and extended 
(var. 8 major Wahl. Fl. Lapp. p. 416) ; and a smaller, with the thallus 
rosulate and stunted (var. pulvinata Mass. Symm. Lich. p. 18). Both 
states are usually well fertile, the apothecia being numerous and often 
crowded. The spermogones have the spermatia vblongo-bacilliform, 
0,030-35 mm. long, 0,007-9 mm. thick. , 
Hab. On caleareous rocks and mortar of walls in maritime and lowland 
districts.— Distr. No doubt general and common, though seen only from 
a few localities in Great Britain —B. M.: Glynde, Sussex ; Anstey’s Cove, 
Torquay, S. Devon; St. Austell, Cornwall ; near Cirencester, Gloucester- 
shire; Great Orme’s Head, Carnarvonshire; Teesdale, Durham: Wark- 
worth Castle, Northumberland. Morningside, near Edinburgh; Appin, 
Argyleshire; near Aberdeen. 
Var. GB. corticicola Nyl. Bull. Soc. Bot. t. xiii. (1866) p. 8366.— 
Thallus smaller, more contracted and less developed, vitelline-yellow 
or greyish-green. Apothecia numerous, congested ; spores (often 
subsimple) -0,011-15 mm. long, 0,005-7 mm. thick.—Cromb. 
Grevillea, xviii. p. 44.—Brit. Exs.: Larb. Lich. Hb. n. 52. 
From the structure of the spores probably referable rather to the next 
subspecies, as suggested by Dr. Arnold (Flora, 1875, p. 158), though also 
approaching subsp. L. tegudaris in external aspect. The plant, as descrihed 
by Nylander, differs from the British specimens in the thallus being 
greyish-green, when the reaction with K 1s less distinct. 
Hab. On the trunk of an elm and on old timber in lowland districts. — 
Distr. Apparently very rare in 8S. and E. England.—B.M.: Windsor 
Great Park, Berkshire ; Great Willbraham, Cambridgeshire. 
Subsp. 1. L. decipiens Nyl. Flora, 1869, p. 81 (nota), 1883, 
p- 106.—Thallus moderate, crowdedly verrucose in the centre, the 
verruce often efflorescent with conculorous soredia, peripheral radii 
