PHYSCIA. 



147 



have somewhat the form of the figure 8, being composed of 

 two large rounded cells, in apposition by one surface : they 

 are of a dark brownish or olive-green colour, and have three 

 coats, the outer being the wall of the primary cell or epi- 

 spore ; the two inner belong to the secondary or contained 

 cellules. The young spores are oval, and full of granular 

 and mucous matter; gradually this becomes divided into 

 two distinct portions by a central septum, and ultimately 

 the bi-cellular condition is produced. This species is also 

 common on the Himalayas, and has been found in other 

 parts of the world. 



3. Physcia prunastri (prunus, a plum-tree). Lacinise 

 flaccid, membranaceous, — above glaucous, reticulate-lacu- 

 nose,- — below white, — linear, divaricate-ramose ; apices acu- 

 minate ; apothecia lateral ; thalamium chestnut-coloured ; 

 margin thin, entire. (E. B. 859.) There is a sorediiferous 

 and a black-punctate form, the latter being var. stictocera. 

 (E. B. 1353.) 



A very common species, pendent on trees and palings in 

 lowland and subalpine districts ; it is extremely abundant 

 on firs in the hill-woods round Perth, coating them with a 

 shaggy beard of grey; but we have only twice found it in 

 fructification. It is very apt to be mistaken for, or con- 



