154 GUIDE TO THE STUDY OF LICHENS. 



turn by black rhizoids. White or light colored soralia 

 occur in a number of the species. As compared with 

 the Physcias the thallus is larger and less distinctly 

 ash-gray, The color varies from gray and brown 

 tinged with green and bluish-green to brown and dark. 



The apothecia are distinctly cup-shaped and vary 

 from medium to very large. It shows perhaps the 

 highest development of the thalline type. It is in 

 reality a secondary thallus having a combined radial 

 and centric structure. The disk is generally brown. 



The spores are simple, colorless, elliptical, often 

 bearing oil-globules ; the spore-wall is thin. 



The Parmelias are common everywhere, occurring 

 upon trees, rocks, stone walls, fences, roofs of old 

 buildings, etc. Some acquire considerable dimensions, 

 reaching three or four feet in diameter. In many cases 

 there is continued marginal growth while the central 

 portion dies away, thus producing a semblance to the 

 "fairy rings" of toad-stools. 



1. Parmelia conspersa. Thallus quite large, growth 

 radial, branched with lobes imbricate (overlapping) ; 

 upper surface usually smooth, sometimes bearing warty 

 outgrowths, soralia rare, brownish to greenish ; lower 

 surface brown with numerous rhizoids. Apothecia 

 small to medium, margin entire. Disk olive-brown. 

 Spores typical, 13/x X Siw- 



2. Parmelia multisporum n. sp. Thallus of medium 

 size, lobed, adnate to substratum ; upper surface smooth 

 and olive color. Apothecia numerous. Disk olive to 

 chestnut-brown; thecae bearing from 50 to 100 color- 

 less elliptical spores, 5/x, X 4/a. 



