196 LECANO-LKCIDKKI [rHIZOCARPON 



over the smooth siirfiicc of the suhstratum, outdistancing the thalline 

 areolre. It predominates also in f. coracinum (Flot. I. c.) wliere the 

 areolae are dark and di{i"use, in f. disjjci'suni Leight. where they are light 

 coloured and scattered, and in f. fusccscens Leight. where the areolae 

 arc also light in colour but contiguous and very thin. 



Hah. On hard rocks, granitic, schistose, or siliceous. — Distr. 

 General and common throughout the ]3ritish Isles. — B. M. St. Boni- 

 face Down, Ventnor, I. of Wight ; Lyndhurst, Hants ; Beeding 

 Downs, Stanmer Park and Hastings, Sussex ; Shiere, Surrey ; High- 

 beach, Epping Forest, Essex ; liosbury Ring and Caer Caradoc, 

 Shropshire ; ^liddletown Hill, Montgomeryshire ; Barmouth and 

 Dolgelly, Merioneth ; Thctford Warren, Norfolk ; Cliffrigg, Louns- 

 dale and Ay ton, Cleveland, Yorkshire ; Portlethen, Kincardineshire ; 

 Ben Lawers, Perthshire ; Morrone, Braemar, Aberdeenshire ; Cork ; 

 Killree, Clare ; Howth, Dublin. 



11. Rh. postumum Th. Fr. Lich. Scand. p. 634 (1874).— 

 Thallus effuse, thin, subgranulose, scattered or evanescent, 

 greyish (K — , CaCl — , medulla I — ). Apothecia subminute, 

 somewhat plane and thinly margined, at length convex and 

 immarginate, black, paraphyses concrete ; epithecium and hypo- 

 thecium brownish ; spores (6-) 8 in the ascus, ellipsoid-oblong, 

 3-septate, usually with a few oblique or longitudinal septa, 

 colourless or at length brownish, scarcely halonate, 0,015-16 mm. 

 long, 0,006-7 mm. thick, or shorter and rather thicker ; hymenial 

 gelatine bluish, the asci wine-red with iodine. — Lecidea postuma 

 Nyl. in Flora li. p. 345 (1868) ; Cromb. in Journ. Bot. vii. p. 50 

 (1869) & Lich. Brit. p. 87 ; Leight. Lich. Fl. p. 328, ed. 3, p. 349. 



A rather obscure plant, related to Rh. confervoides, of which 

 Nylauder says it would almost appear to be a starved condition, with 

 smaller spores. In the two specimens gathered the thallus is scarcely 

 visible, except around the somewhat scattered apothecia. 



Hah. On calcareous stones among detritus in an alpine situa- 

 tion. — B. M. Ben Lawers, Perthshire. 



12. Rh. distinctum Th. Fr. Op. cit. p. 625. — Thallus greyish 

 or brownish, minutely areolate, the areola? plane or slightly convex 

 ( K — or slightly brownish, CaCl — ) ; hypothallus black. Apothecia 

 rather small, depressed, plane, thinly margined or immarginate ; 

 hypothecium purplish-brown ; paraphyses slender, involved in 

 mucus, purplish-brown at the tips ; spores oblong, ellipsoid, or 

 irregular in form, colourless, becoming pale-olive, 1-5-septate and 

 muriform, halonate, 0,024-32 mm. long, 0,012-15 mm. thick; 

 hymenial gelatine deep-blue with iodine. 



Differs from Rh. confervoides in the purple colour of hypothecium 

 and epithecium. 



Hah. On granitic or sandstone rocks, rare. — B. M. Morrone, 

 Braemar, Aberdeenshire. 



13. Rh. obsciiratum Massal, Ric. Lich. p. 103 (1852). — 

 Thallus greyish- or pale-brown, thin, minutely areolate, the 

 areolae contiguous or dispersed, nearly plane, sometimes evan- 



