142 GUIDE TO THE STUDY OF LICHENS. 



5. Theloschistes. 



The thallus varies from almost foliose to fruticose. 

 The fruticose forms are much branched and usually 

 bear long grayish cilia along the margin of the lobes. 

 Usually there is more or less of a yellowish tinge ; in 

 some only a grayish color. Soralia are less common 

 than in Physcia. 



The apothecia are discoid, usually larger than in 

 Physcia. Disk orange, yellowish, in some species dark- 

 gray to nearly black. The spores resemble those of 

 Placodium, from which this group is perhaps pliylo- 

 genetically derived. 



The Theloschistes are more southern and western 

 than the Physcias. They occur upon bark, rock, old 

 walls, fences, old buildings, etc. Frequently they are 

 associated with species of Physcia. 



1. Theloschistes polycarpus. Thallus foliose, lobe 

 short, rounded, dirty lemon to orange. Apothecia 

 usually small, very numerous, the entire margin of 

 the thallus studed with them. Disk concave, orange. 

 Spores colorless, typical, 15^ X 8/a. 



2. Theloschistes lychneus. Thallus foliose, branch- 

 ing, lobes broad and more or less ascending, soralia 

 often present; orange above, lighter color beneath. 

 Apothecia rare, medium size. Disk flattened, red- 

 dish-brown. Spores colorless, typical, 12/x X 8.5/x. 



3. Theloschistes concolor. Thallus foliose, minutely 

 branching, lobes of uniform width, not ascending, 

 greenish-yellow above, gray beneath. Apothecia of 

 medium size, cup-shaped, margin somewhat fibrillose. 

 Disk of the same color as thallus. The spores are 



