492 



LICHENACEI. 



[PERTTJSARIA. 



Soc. Cherb. iii. p. 180. Thallus continuous, verrucoso-unequal, or 



smoothish, very rarely hypophlceodal. Apothecia endocarpoid or 



lecanoroid ; spores l-4uae, 6-8na3, 



large, ellipsoid or oblong, colourless, 



rarely blackish, with a thick or 



thickish epispore ; paraphyses lax or 



coherent, variously branched and 



arcuate ; hy menial gelatine, but chiefly 



the thecse, deep-lilac with iodine. 



Spermogones with acicular, straight 



spermatia. 



A natural and well-defined genus, 

 most of the European species of which 

 occur in our Islands, where also one or 

 two seem to be endemic. Several of the 

 plants included in it frequently occur 

 only in a variolarioid or isidioid state, 

 constituting the pseudogenera Variolaria 

 and Isidium of older authors. A few of 

 these enumerated by Turner and Borrer 

 in their ' Lichenographia Britanuica ' 

 and subsequently figured in Eng. Bot. 

 Suppl., being very doubtful, are here 

 omitted. 



A. Theca3 pauci-spored ; spores colour- 

 less. 

 a. Spores solitary. 



1. P. bryontha Nyl. Lich. Scand. 

 (1861) p. 178 ; Flora, 1881, p. 538. 

 Thallus effuse, thin, subgranulato- 

 unequal, white or whitish, white-sore- 

 diose (K + yellowish, soredia CaCl-f- 

 reddish). Apothecia lecanorine, mode- 

 rate, at first urceolate, then subplane, 

 prominent or substipate, opaque, 

 sordidly liver-coloured, or sordid- 

 brownish, the thalline margin at 

 length depressed or excluded ; spores 0,1500,230 mm. long, 

 0,050-70 mm. thick. Cromb. Lich. Brit. p. 58 ; Leight. Lich. Fl. 

 p. 240, ed. 3, p. 230. Parmelia subfusca ft. bryontha Ach. Meth. 

 (1803) p. 167. Pertusaria macrospora Hepp, Mudd, Man. p. 277. 



Looks almost a state of Lecanora epibrya, but is very different in the 

 structure of the fruit and the form of the spermatia. The apothecia, 

 which are at first pale, are in our few specimens at times somewhat 

 crowded. It is one of our rarest British lichens. 



Hab. On the ground, encrusting mosses and decayed Carices, in alpine 

 places. Distr. Extremely local and scarce on one or two of the N. 

 Grampians, Scotland. B. M. : Cairngorm and Ben-naboord, Braernar, 

 Aberdeenshire. 



X-2.BO 



Fig. 70. 



Pertusaria communis DC. 

 A 2-spored theca and para- 

 physes, X 250. 



