146 GUIDE TO THE STUDY OF LICHENS. 



The apothecia are quite small, globose, and are 

 immersed in the thallus, opening by a pore. The 

 hypothecium is usually dark. The genus should 

 perhaps be placed with the VerriicariacecE, since 

 its apothecial characters point toward such a relation- 

 ship. 



The spores, when mature, are multilocular and 

 dark. The immature spores are simple, colorless, and 

 larger than the mature spores. It should also be 

 borne in mind that the mature spores are often quite 

 structureless. 



Most of the species are northern in their range. 

 They occur upon rocks, a few upon the soil. 



1. Urceolaria actinostoma. Thallus comparatively 

 thin, areola te, areoles never convex ; gray to dark-gray. 

 Apothecia small, immersed in somewhat convex areoles. 

 Disk dark. Spores dark, multilocular, 14)u, X 7.5/x. 



2. Urceolaria scruposa. Thallus quite thick, areo- 

 late, fissured, gray. Apothecia immersed in somewhat 

 elevated areoles. Disk somewhat darker than thallus. 

 Spores dark-brown, elliptical, multilocular, 21/jt X 9/a. 



An orange coloring substance is obtained from the 

 Urceolarias ; it was used in dyeing woollen goods. 



2. Hcematomma. 



This genus is usually combined with Lecanora, 

 though its spore-characters are wholly different. The 

 thallus is crustose but very thick; sometimes covered 

 over by a soredial powder. The color is gray tinged 

 with green, or sometimes yellowish. 



The apothecia vary from medium to quite large; 



