THBLIDIUm] VERRUCARIACEiE 297 



106. THELIDIUM Massal. Framm. Lich. p. 15 (1855). 

 (PL 42.) 



Thallus variously crustaceous, uniform, sometimes wanting. 

 Algal cells Pleurococcus. Perithecia black, simple, superficial or 

 immersed ; paraphyses mucilaginous, soon disappearing ; asci 

 usually somewhat large and saccate, 8-spored ; spores ellipsoid or 

 ovoid, usually rather large, 2-4:-celled, colourless or sometimes 

 brownish. 



Spores l-septaie. 



1. Th. pyrenophorum Koerb. Syst. Germ. p. 353 (1855) pro 

 parte, emend, (non Massal.). — Thallus greyish-white or -brown, 

 effuse, thin, slightly cracked when old, sometimes almost obsolete. 

 Perithecia rather large, semi-immersed or superficial, usually 

 depressed round the ostiole ; perithecial wall thick, dimidiate, 

 the inner wall brownish ; paraphyses disappearing ; spores broadly 

 oblong, colourless or pale-yellowish, 1-septate, 0,020-32 mm. long, 

 0,010-18 mm. thick.— TA. Borreri Mudd Man. p. 296 (1861). 

 Verrucaria pyrenophora Ach. Lich. Univ. p. 285 (1810) ; V. 

 Dufourii Borr. in Engl. Bot. Suppl. t. 2791 (1831) (non DC.) ; 

 Tayl. in Mackay Fl. Hib. ii. p. 92; Leight. Angioc. Lich. p. 51. 

 F. Borreri Leight. tom. cit. p. 76, t. 22, fig. 4 (1851) & Lich. Fl. 

 p. 429 ; ed. 3, p. 459 ; Cromb. Lich. Brit. p. 112 pro parte. 



From the similarity in the outward formation of thallus and 

 especially of the perithecia, when well developed apt to be confused 

 with Th, papulare and Verrucaria Dufourii. 



Hah. On calcareous rocks. — Distr. Eare in Scottish Grampians 

 and W. Ireland. — B. M. Ben Lawers, Perthshire ; Morrone, Braemar, 

 Aberdeenshire ; Clifden, Connemara, Galway. 



2. Th. mesotropum A. L. Sm. — Thallus pale, thin, unequal. 

 Perithecia black, somewhat turgid, convex ; perithecial wall 

 dimidiate ; spores colourless, ovoid or ovoid-oblong, small, 

 1-septate, 0,012-17 mm. long, 0,005-6 mm thick; hymenial 

 gelatine wine-red with iodine. — Verrucaria mesotropa Nyl. in 

 Flora Ixix. p. 419 (1866) ; Leight. in Ann. Mag. Hist. ser. 3, 

 xix. p. 408 (1867) & Lich. Fl. p. 431 ; ed. 3, p. 459 ; Cromb. 

 Lich. Brit. p. 115. 



Hah. On subalpine rocks. — Distr. Bare in hilly districts in W. 

 England and Wales. — B. M. Llanymynech Hill, Shropshire. 



3. Th. immersum Mudd Man. p. 295, t. 5, fig. 123 (1861).— 

 Thallus white, grey-ashy-white or pale-dirty-yellow, thin, tar- 

 tareous and somewhat farinose, sometimes determinate. Peri- 

 thecia black, deeply immersed and leaving pits in the rock, 

 depressed round the ostiole ; perithecial wall thick above, thinner 

 round the base ; spores colourless, ellipsoid, constantly 1-septate, 

 rather large, 0,025-38 mm. long, 0,012-17 mm. thick.— Ferrw- 

 caria immersa Leight. Angioc. Lich. p. 57, t. 25, fig. 2 (1851) 



