7(5 LICHENES. [Spiloma. 



1. Lepraria. Ach. 



Thallus crustaceo-leprose, uniform, effuse. Apothecia none. 

 Gongyli naked, covering the thallus, more or less scattered. 



The very first of our list is the most unsatisfactory and doubtful of 

 the Genera of Lichens. Its present use appears to arise from its 

 being a depository of certain species, with a powdery thallus, whose 

 fructification is unknown. Lepraria incana of Ach. Lich. Univ. is 

 now ascertained to be a Lecidea ; whilst L. ceruginosa, Eng. Bot. 

 and L. chlorina Ach. have been removed by Dr. Hooker to the 

 Fungi. 



1. L. viridis, Turn, and Borr. Crust none; gongyli minute, 

 usually clustered, bright green, globular, somewhat unequal in 

 size, forming an irregularty continuous, thin, powdery mass. 

 Turn, and Borr. Lich. Br. p. 6, ( according to Hooker in Eng. Flor. 

 vol. 5, p. 163;, L. botryoides Eng. Bot. t. 2148. 



On trees, pales, and walls ; common. On alders a membranous, 

 and in wet weather a subgelatinous substratum of a duller green is 

 sometimes observable, but whether truly belonging to the species is 

 uncertain, as it commonly occurs without any such appearance. 



2. L. fiava, Ach. Crust none ; gongyli minute, of a bright 

 yellow, forming an irregularly continuous crustaceous powdery 

 mass. Ach. Lich. Un. p. 663. Eng. Bot. t. 1350. 



On old trees ; not uncommon. Near Belfast, Mr. Templeton. The 

 crust is thinner on the pines than on old oaks. 



3. L. alba, Ach. Crust grey, edged with white downy fibres ; 

 gongyli extremely minute, snow white, forming continuous 

 crustaceous patches. Ach. Meth. p. 3. Eng. Bot. t. 1349. 



On trunks of trees and on mosses ; common. The crust is denser 

 than in the preceding, and in the herbarium almost entirely loses its 

 snow-white colour. 



4. L. Iolithus, Turn, and Borr. Crust filmy, greyish ; gon- 

 gyli extremely minute, of a purplish red, forming a thin even 

 powdery mass. Turn, and Borr. Lich. Br. p. 21, [according to 

 Hook. Eng. Flor. vol. 5, p. 164). Eng. Bot. t. 2471. 



On stones ; Deer Park wall, near Belfast, Mr. Templeton. 



2. Spiloma. Ach. 



Thallus crustaceous, uniform, effuse, usually thin, continuous. 

 Apothecia none, (that is without any subgelatinous parenchy- 

 ma). Gongyli collected into compact masses, coloured, naked. 

 In Lepraria the Gongyli constitute the entire thallus — in fact, 

 almost the entire Lichen ; but in Spiloma they constitute the col- 

 lections similar to Apothecia, upon a thallus of a different nature and 

 structure. In the specific characters these collections are termed 

 Apothecia. 



