LBCIDEA] LECIDEACEjE 87 



oblong-ellipsoid, 0,006-8 mm. long, 0,003-4 mm. thick ; hymenial 

 gelatine pale-bluish then tawny-wine-red with iodine. — Cromb. 

 in Journ. Bot. xx. p. 275 (1882). L. perustula Nyl. I. c. p. 221 ; 

 Cromb. in Grevillea viii. p. 29. L. nitida Leight. Lich. Fl. ed. 3, 

 p. 295 pro parte (non Schser.). 

 Exsicc. Leight. n. 278. 



Resembles a diminutive state of L. fuscoatra, differing in the 

 absence of any thalline reactions and the much smaller spores. The 

 numerous inconspicuous apothecia occasionally have the margins 

 paler. 



Sab. On siliceous rocks in maritime and mountainous districts. — 

 Distr. Only a very few localities in Wales and W. Ireland ; probably 

 overlooked elsewhere. — B. M. Barmouth, Merioneth ; Llanberis, 

 Carnarvonshire; Dunkerron, Kerry; Doughruagh Mt., Connemara, 

 Galway. 



151. L. rivulosa Ach. Meth. p. 38 (1803) ; Nyl. Lich. 

 Scand. p. 222. — Thallus determinate, areolate-rimose or granulate- 

 areolate, mouse-coloured, greyish-brown or pale-greyish (K — , 

 CaCl — ) ; hypothallus blackish, limiting and intersecting the 

 thallus. Apothecia sessile, or adnate, somewhat plane, margined, 

 slightly scabrid, brownish-black or black, the margin thin, 

 flexuose, paler, paraphyses discrete, brown at the apices ; hypo- 

 thecium pale ; spores ellipsoid or ellipsoid-oblong, slightly curved, 

 0,009-12 mm. long, 0,004-6 mm. thick ; hymenial gelatine pale- 

 bluish, the apices of the asci deep-blue then wine-red with iodine. 

 — S. r. Gray Nat. Arr. i. p. 467 ; Hook, ia Sm. Engl. PL v. 

 p. 179 ; Tayl. in Mackay PL Hib. ii. p. 125 ; Mudd Man. p. 199 

 (excl. var.) ; Cromb. Lich. Brit. p. 79 ; Leight. Lich. PI. p. 285 ; 

 ed. 3, p. 291. Lichen rivulosus Sm. Engl. Bot. t. 1737 (1807). 



Exsicc. Leight. n. 302; Mudd n. 168; Larb. Lich. Hb. 

 n. 309 ; Johns, n. 353. 



Easily recognized by the brownish-black hypothalline lines with 

 which the thallus is usually intersected, and which suggested the 

 trivial name. When the thallus is more granulose, the granules are 

 depressed, plane, and either contiguous or discrete (f. depressa Leight. 

 ed. 3, p. 291). Very rarely it is evanescent, the hypothallus and 

 fructification only being visible (f. depauperata Leight. i. c). The 

 numerous though scattered apothecia are in moist situations often 

 brownish-flesh-coloured, but become darker in the herbarium. , The 

 spermogones are frequent, verrucseform, scattered or confluent, with ■ 

 spermatia oblong, 0,003-4 mm. long, 0,001 mm. thick. 



Hab. On rocks, chiefly granitic and quartzose, in maritime and 

 mountainous districts. — Distr. Rather local, but plentiful where it 

 occurs, in the Channel Islands, S., W. and N. England, Wales, 

 Scotland and N.W. Ireland. — B. M. Sark and Guernsey ; near 

 Haytor, Dartmoor, Devon ; Rosoorla and Kymyal Cliff, Penzance, 

 Cornwall ; near Seaford, Sussex ; Mynydd Gader, Dolgelly, Bar- 

 mouth, and Cader Idris, Merioneth; Holyhead, Anglesea; Kildale 

 Moor, Cleveland, Yorkshire ; the Cheviots, Northumberland ; Bar- 

 caldine and Appin, Argyll; Crianlarioh, Ben Lawers, and Ben-y-gloe, 



