LiXANoijA.] i.i;tA.\(j-i,ix'iDEi:i. 350 



11. L. muroruin Ach. Lich. Univ. (l81o) p. 44:3; Xyl. Flora, 

 1883, p. lU(j. — Thallus orbicular, cloocly adiiate, usually whitish- 

 sufFused, subrimo.so-areolate in the centre, plicato-radiose at the 

 circuinforenco, 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,OUU-lo mm. 

 long, 0,O()4-7 mm. thick. — Cromb. Grevillea, xviii. p. 44 ; Hook. 

 Fl. Scot. ii. p. 5U pro parte; Tayl. in Mack. Fl. Hib. ii. p. 140 

 pro parte. — P/itcodiam muronua Leight. Lich. Fl. p. 17'5 pro parte, 

 ed. 3, p. 161 pro parte ; Cromb. Lich. lirit. p. 45 pro parte ; Mudd, 

 Man. p. 132 pro parte ; Gray, Nat. Arr. i. p. 447 pro parte. 8(jita- 

 mnria murorum Sm. Eng. Fl. v. p. 194 pro parte. Lichen murorum 

 HofFm. Enum. (1784) p. 03 ; Eng. But. t. 2 157 (lower fig.). Lichen 

 Jlavescens Huds. Fl. Augl. p. 445 pro parte. 



A species until recently little understood and very impf^vfectly limited, 

 so that tlie trivial name of muroruni, as applied to it by British and other 

 authors, is, to a great extent, a tiom/'n vagutn. It appear:^ under two con- 

 ditions of growth — a larger, with the thallus more developed and extended 

 tvnr. ^ m-'jor Wahl. Fl. Lapp. p. 41G) ; and a snialler, with the thallus 

 rosulate and stunted (var. pidrinata Mass. Symni. Lich. p. 1.3). liuth 

 states are usually well fertile, the apothecia being numerous and often 

 crowded. The spermogones have the spermatia ubloDgo-bacilliform, 

 0,0;J0-;J-5 mm. long, 0,007-9 mm. thick. 



Hah. On calcareous 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, Sus.sex ; Anstey's Cove, 

 Torquay, S. Devon ; St. Austell, Cornwall ; near Cirencester, Glouce.-ter- 

 shire ; Great Orme's Head, Carnarvonshire : Teesdale, Durham ; Wark- 

 worth Castle, Northumberland. Morniiigside, near Edinburgh ; Appin, 

 Argyleshire ; near Abeideen. 



Var. /3. corticicola Xyl. Bull. Soc. Bot. t. xiii. (1SG6) p. 36(1 — 

 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, 187-5, p. lo3), though al>o 

 approaching subsp. L. ter/ulari-^ in external aspect. The plant, as described 

 by Nylander, ditiers from the British specimens iu the thallus being 

 greyish-green, when the reaction with K is less distinct. 



Hah. On the trunk of an elm and on old timber in lowland districts. — 

 Distr. Apparently very rare in S. and E. England.— B. M. : Windsor 

 Great Park, Birkshire ; Great Willbraham, Cambridgeshire. 



Subsp. 1. L. decipiens Xyl. Flora, 1869, p. 81 (nota), 1883, 

 p. 106. — Thallus moderate, crowdedly verrucose in the centre, the 



vorruoic often efflorescent with concolorous sorcdia, periphei'al radii 



