rhizocaepon] lecideace^ 189 



and iinmarginate. In var. jyojuiloruni {Diplotomma populorum 

 Massal. liic. Lich. p. 99 (1852) ; Lecidea parasema var. atliroa Ach. 

 Meth. p. 36) the thallus is limited and forms whitish patches on the 

 trunks of poplars and other trees, occasionally also on rocks. 



Hah. On trees and palings.— Dts^r. General and common in 

 England and the Channel Islands. Apparently rare in Scotland, not 

 iinfrequent in Ireland. — B. M. Shanklin, I. of Wight ; Bovey Traccy, 

 Devon ; near L^'mington, Hants ; Ightham, Kent ; St. Leonard's 

 Forest, and Elmer, Middleton, Sussex ; Braxted Park, Langford and 

 Quendon, Essex ; near Cheltenham and Sapperton, near Cirencester, 

 Gloucestershire ; Windsor Great Park, Berks ; Nannau, Dolgelly, 

 Merioneth ; Twycross, Leicestershire ; Montford Bridge near Shrews- 

 bury, Oswestry ; Wafield, Shropshire ; near Alfrock Churchhill, 

 Kempsey and Spelchley, Worcestershire ; Tetsworth, Oxfordshire ; 

 Seething, Norfolk ; Ettersgill, Teesdale, Durham ; Sowerdale, Cleve- 

 land, Easby and Ayton and near Masham, Yorkshire ; Airds House 

 Appin, Argyll ; Finlarig, Killin, Perthshire ; Limerick, Clare. 



Var. venustum A. L. Sm. — Thallus thiekish, white. Apothecia 

 somewhat larger, immersed, then emerging and subconvex, with 

 a spurious white margin. — Diplotomma venustum Koerb. Parerg. 

 Lich. p. 179 (1860). Lecidea calcarea Leight. Lich. Fl. p. 327 ; 

 ed. 3, p. 348 (non Lichen calcarius Weis). 



Hab. On rocks. — Distr. Eare in the Channel Islands, S. England, 

 Scotland ? and W. Ireland, — B. M. Green Island, Jersey ; near 

 Penzance, Cornwall ; Killree, Clare. 



Var. epipolia A. L. Sm. — Thallus white, effuse or limited, 

 tartareous, cracked-areolate or subpulverulent. Apothecia black, 

 white- or bluish-grey -pruinose, immersed, then erumpent, at first 

 plane, becoming convex, with or without a proper margin, often 

 with a spurious thalline margin. — Lichen epipolius Ach. Lich. 

 Suec. Prodr. p. 58 (1798) ; Engl. Bot. t. 1137. Lecidea epipolia 

 Ach. Moth. p. 53 (1803); S. F. Gray Nat. Arr. i. p. 468. 

 L. alhoatra var. eplpjolia Sch^er. Enum. p. 122(1850); Cromb. 

 Lich. Brit. p. 87 ; £. epipolia Leight. Lich. Fl. p. 327 ; ed. 3, 

 p. 347. Diplotomma alboatrum var. cpipolium Mudd Man. p. 218 

 (1861). 



Exsicc. Leight. n. 241 ; Mudd n. 193 ; Larb. Lich. Hb. nos. 

 177, 178 (as var. amhigua) ; Carroll Lich. Hib. n. 21; Johns, 

 n. 357. 



Often with the appearance of a Lecanora owing to the immersed 

 apothecia being closely surrounded by the thallus. A number of 

 forms have been recorded by Leighton and others characterized by 

 various states of the apothecia and of thalline development ; — f. mar- 

 garitacca Leight. I. c. {Lecidea margarltacea Ach. Lich. Univ. p. 185 

 (1810) pro parte ; S. F. Gray Nat. Arr. i. p. 468), the apothecia are more 

 deeply immersed, with a somewhat more pronounced thalline margin ; 

 in f. murorum Leight. I. c. p. 348, the apothecia are minute and 

 also deeply iniinersed, the thallus thin and pale-yellowish ; f. amhigua 

 Leight. I. c. {Lecidea amhigua Ach. Lich. Univ. p. 161) has a thin 

 cracked sometimes dispersed greyish thallus, the apothecia becoming 

 superficial and with a proper margin only. 



