152 GUIDE TO THE STUDY OF LtCHENS. 



Jf.. Acarospora. 



This genus is by some authors placed with Lecanora. 

 The thallus is crustose and rudimentary in the lower 

 forms ; in the higher forms it becomes foliose and 

 lobed, especially toward the margin. In many re- 

 spects the thallus resembles that of Hcematomma. 

 Color dark in the lower forms and yellowish in some 

 of the higher forms. Algas are Pleurococcus vulgaris 

 as in Endocarpon. 



The apothecia are immersed in the thallus, variable 

 in size and form. The disk varies from orbicular to 

 irregularly lobate or. crenate ; it is usually flattened, 

 more rarely convex, or margin slightly elevated. 

 Color of disk varies from dark to yellowish. The 

 spore-sacs are cylindrical, and each one contains sev- 

 eral hundred very minute simple colorless spores 

 which are held together by a gelatinous substance, 

 so that the entire contents may be ejected or forced 

 out. 



The Acarospora are quite widely distributed and 

 occur principally upon rock (granite) and sandy soil. 



1. Acarospora privigna. Thallus rudimentary, yel- 

 lowish to dark. Apothecia small, orbicular, scattered ; 

 margin slightly elevated above the dark flat disk. 

 Spores elliptical, typical, 3/a X l-^i^- 



2. Acarospora cervina. Thallus areola te, dark to 

 nearly black. Apothecia barely raised above the 

 thallus, often remaining after the thallus is worn 

 away, irregular in outline. Disk dark. Spores 

 closely adherent owing to a gelatinous substance, 

 typical. 



