POLYBLASTIA] VBKRDCAEIAOBfi 301 



Perithecia moderate in size, black, prominent, immersed at the 

 base, subhemispherical, usually somewhat depressed round the 

 poriform ostiole ; perithecial wall dimidiate ; paraphyses none ; 

 spores 8 in the ascus, colourless, rarely pale brownish, ellipsoid, 

 muriform, the cells numerous, irregular, 0,024-42 mm. long, 

 0,015-21 mm. thick ; hymenial gelatine wine-red with iodine. — ■ 

 Verrucaria intercedens Nyl. in Maine et Loire Mem. Soc. Acad, 

 iv. p. 33 (1858);, Carroll in Journ. Bot. iii. p. 292 (1865); 

 Cromb. Lich. Brit. p. 114; Leight. Lich. H. p. 454; ed. 3, 

 p. 487. 



Very variable in appearance according to the form of development. 

 In some specimens the perithecia are strongly umbilicate and are 

 comparable with those of Verrucaria Dufourii or Thelidium papulare ; 

 in others the ostiole is scarcely visible. 



Hah. On schistose, arenaceous and calcareous rocks. — Distr. Bare 

 in mountainous regions in Scotland and N. England, but also recorded 

 from S. England. — B. M. Buxton, Derbyshire ; Ben Lawers, Perth- 

 shire. 



2. P. spurcella A. L. Sm. — Very similar to the preceding, 

 except for the thinner, obscurely smoky thallus ; spores colourless, 

 murali-locular, 0,022-25 mm. long, 0,011-14 mm. thick. — Verru- 

 caria spurcella Nyl. ex Shackleton &, Hebden in Naturalist, 

 1892, p. 17. Specimen not seen. 



Hab. Limestone walls (Malham, Gordale, Yorkshire). 



3. P. fuscoargillacea Anzi in Oomm. Soc. Critt Ital. ii. 1, 

 p. 26 (1864). — Thallus brownish- or whitish-grey, thin, effuse, 

 minutely cracked-areolate, becoming farinose. Perithecia black, 

 small, numerous, often crowded, sessile, hemispherical, the base 

 only immersed, the ostiole poriform ; perithecial wall dimidiate ; 

 paraphyses disappearing; spores ,6 to 8 in the ascus, ellipsoid, 

 colourless or faintly yellowish, muriform, 0,018-28 mm. long, 

 0,011-16 mm. thick; hymenial gelatine reddish with iodine. — 

 Verrucaria fuscoargillacea Cromb. in Journ. Bot. ix. j). 179 

 (1871) ; Leight. Lich. Fl. p. 455 ; ed. 3, p. 487. 



Hab. On rocks, mostly calcareous. — Distr. Rare in W. England, 

 N. Scotland and W. Ireland. — B. M. Craig TuUoch, Blair Athole, 

 Perthshire. 



Spores colourless becoming brownish. 



4. P. Schraderi A. L. Sm. — Thallus greyish - white, thin, 

 tartareous and somewhat farinose. Perithecia black, globose, 

 deeply immersed and leaving pits in the rock, the ostiole only 

 slightly emerging ; perithecial wall entire ; spores 8 in the ascus 

 ellipsoid, muriform, usually 3-septate with an irregular longitu- 

 dinal division, colourless, becoming brownish, about 0,040-45 mm. 

 long, 0,012-17 mm. thick. — Lichen Schraderi Sm. Engl. Bot. 



