300 PYEENOCARPEI [tHELIDIUM 



Doubtful or parasitic. 



9. Th. sparsulum A. L. Sm. — Thallus indistinct. Perithecia 

 scattered, minute, subglobose ; perithecial wall entire ; asci some- 

 what saccate ; parapfiyses mucilaginous, disappearing ; spores 

 colourless, ellipsoid, becoming 3-septate, 0,023-27 mm. long, 

 0,010-13 mm. thick. — Verrucarina sparsula Nyl. in Flora Ix. 

 p. 231 (1877) ; Cromb. in Grevillea vi. p. 20. Verrucaria sparsula 

 Leight. Lich. Fl. ed. 3, p. 478. 



The extremely minute perithecia are scattered over the substratum 

 either on the stone or on a thinlj- furfuraceous dark-brownish layer, 

 a mixture of various algfe and brown fungal hyphse. Kvlander {I. c.) 

 considered the blue-green algse to be gonidimia and described the 

 lichen under a new genus Verrucarina akin to Pyrenidiaceae. The 

 specimens in the British Museum are somewhat imperfectly developed ; 

 the connection is not clear between the perithecia and the gonidimia, 

 and the spores are immature and simple or only 1-septate. 



Hab. On chalk. — Distr. Rare in S. England. — B. M. Lewes, 

 Sussex ; Dorking and Keigate, Surrey. 



10. Th. superpositum A. L. Sm. — ThaDus none. Perithecia 

 minute, almost superficial, black, depressed globose, with a pori- 

 form ostiole ; perithecial wall entire ; paraphyses mucilaginous, 

 disappearing ; ostiolar filaments (periphyses) distinct ; asci obo- 

 vate-ellipsoid ; spores 8 in the ascus, colourless, ellipsoid-clavate, 

 1-septate, 0,017-19 mm. long, 0,006-8 mm. thick; hymenial 

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

 Flora xlviii. p. 3-57 (1865); Carroll in Journ. Bot. iv. p. 25 

 (1866); Cromb. Lich. Brit. p. 115; Leight. Lich. Fl. p. 462; 

 ed. 3, p. 494. 



Hab. Parasitic on Polyblastia theleodes. — B. M. Ben Lawers, 

 Perthshire (the only locaUty). 



107. POLYBLASTIA Massal. Ric.*Lich. p.l47(lS52); emend. 

 Lonnr. in Flora xli. p. 630 (1858). — Sphseromphale Reichenb. 

 Consp. Reg. Veg. p. 20 (1828) pro parte; Mudd Man. p. 281 

 pro parte. (PI. 43.) 



Thallus variously crustaceous, not corticated, sometimes 

 developed within the substratum. Algal cells Pleurococcus. 

 Perithecia simple, superficial or immersed in the thallus, some- 

 times embedded in the substratum and leaving pits ; ostiole a 

 simple pore ; paraphyses mucilaginous, disappearing ; asci broadly 

 clavate, 1-8-spored ; spores rather large, ellipsoid, muriform, 

 colourless or dark-coloured. 



Spores colourless. 



I. P. intercedens Lonnr. in Flora xli. p. 631 (1858).— Thallus 

 greyish or dark-brownish, tartareous, thin, continuous or faintly 

 cracked, effuse or determined by a black line, sometimes obsolete. 



