FUNGI. 



75 



filaments, the whole separating spontaneously from the plant and giving 

 rise to a new one. 



Owing to the toughness of the filaments, the finer structure 

 of the lichens is often difficult to study, and free use of caustic 

 potash is necessary to soften and make them manageable. 



According to their form, lichens are sometimes divided into 



FIG. 45. Forms of lichens. A, a branch with lichens growing upon it, one- 

 half natural size. B, Usnea, natural size. ap. spore fruit. C, Sticta, one- 

 half natural size. D, Peltigera, one-half natural size. ap. spore fruit. E, a 

 single spore fruit, x 2. F, Cladonia, natural size. G, a piece of bark from 

 a beech, with a crustaceous lichen (Graphis) growing upon it, x 2. ap. spore 

 fruit. H, Soredium of a lichen, x 300. 



the bushy (f ruticose), leafy (frondose), incrusting (crustaceous), 

 and gelatinous. Of the first, the long gray Usnea (Fig. 45, 

 A, B), which drapes the branches of trees in swamps, is a 

 familiar example ; of the second, Parmelia, Sticta (Fig. 45, O) 

 and Peltigera (D) are types ; of the third, Graphis (G), common 

 on the trunks of beech-trees, to which it closely adheres ; and 



