TEETUSARIA.] LECANO-LECIDEEI. 509 



27. P. gyrocheila Nyl. Flora, 1865, p. 354. Thallus deter- 

 minate, subgranuloso-unequal, rimoso-diffract, greyish (K + yellow, 

 CaCl ). Apothecia in thelotremoid tubercles, simple or at 

 length subgyrose, the thalline margin thick, stibgyrose ; epithecium 

 glypholeceine, hymenium pale ; spores 0,068-70 mm. long, 0,036- 

 50 mm. thick ; hymenial gelatine and the thecae bluish with 

 iodine. Carroll, Journ. Bot. 1866, p. 23 ; Cromb. Lich. Brit, p 61 

 Leight. Lich. Fl. p. 241, ed. 3, p. 232. 



A very distinct species well characterized by the peculiar form of the 

 fructification. The thallus is small, with the fertile verruca? more or less 

 scattered and crateriform. The very few specimens gathered are only 

 sparing fertile. 



Hob. On mica-schist rocks in an alpine situation. Distr. Extremely 

 local and scarce on one of the S. Grampians, Scotland. B. M. : Summit 

 of Ben Lawers, Perthshire. 



6. Spores normally 4nae. 



28. P. leioplaca Schaer. Spicil. (1823) p. 66 ; Nyl. Lich. Scand. 

 p. 181. Thallus subdeterminate, thin or rarely submoderate, 

 smooth or ruguloso-unequal, rimose, milk-white, yellowish-white 

 or whitish (K orf+ yellowish). Apothecia in somewhat convex, 

 smooth, usually discrete verrucae, the ostioles solitary or few 

 (1-3-5), punctiform, dark ; spores usually 4nse (but variable in 

 number), oblongo- ellipsoid or subellipsoid, 0,042-75 mm. long, 

 0,020-38 mm. thick. Mudd, Man. p. 267; Cromb. Lich. Brit, 

 p. 60 ; Leight. Lich. Fl. p. 244, ed. 3, p. 234. Porina leioplaca 

 Ach. Vet. Ak. Handl. 1809, p. 159 ; Lich. TJniv. p. 309, t. 7. f. 2. 

 Pertusaria communis var. S. leioplaca Turn. & Borr. Lich. Br. 

 p. 197. Brit. Exs. Leight. n. 230 ; Mudd, nos. 265, 267. 



The thallus varies somewhat in thickness, becoming at times subcon- 

 crescent, when the verrucae are more prominent. As noted by Th. M. 

 Fries (Lich. Scand. p. 316), the chemical reaction varies according to the 

 colour of the thallus, being little (or not) distinct when it is dealbate. 

 The apothecia are also variable, usually solitary, rarely 3 or o in the 

 verrucae, with the spores at times 3-5-6-8na3, very rarely 2na3 (in a 

 single British specimen). 



Hab. On the trunks of trees in maritime and upland districts. Distr. 

 In most parts of Great Britain, no doubt also of Ireland ; not seen from 

 the Channel Islands. B. M. : Near Highbeach, Epping Forest; Ightham, 

 Kent ; St. Leonard's Forest, Sussex ; Shanklin, Isle of Wight ; New 

 Forest, Hants ; Lustleigh, S. Devon ; "Withiel, Cornwall ; near Ciren- 

 cester, Gloucestershire ; Woodbury Hill and Malvern, Worcestershire ; 

 Gopsall Park, Leicestershire ; Gloddaeth, Carnarvonshire ; Bettws-y- 

 coed, Denbighshire ; Island of Anglesea ; Newton Wood and Sowerdale, 

 Cleveland, Yorkshire: Lamplugh, Cumberland. Barcaldine, Argyle- 

 shire ; Craig Calliach, Killin and Falls of Moness, Aberfeldy, Perthshire ; 

 Moor of Morrone, Braemar, Aberdeenshire ; Glen Nevis, Inverness-shire. 

 Enniskean, co. Cork ; McCarthy's Island and Upper Lake, Killarney, co. 

 Kerry ; Renvyle Wood, Conneniara, co. Galway. 



