GENERA AND SPECIES. 153 



This plant is often found associated with species of 

 Placodium. 



3. Acarospora dealbata. Thalhis of white scattered 

 warts of considerable .thickness. Apothecia immersed, 

 one in each areole. Disk black. Spores typical. 



5. Speer Schneider a. 



This genus, as represented by the single species, is 

 closely related to Parmelia. The thallus is foliose, much 

 branched, with lobes of uniform width. There is also 

 a slight fruticose tendency. The apothecia are rather 

 small, sessile upon the upper surface of the thallus. 

 Disk light-brown. The spores are small, colorless, 

 elliptical and distinctly two-celled. 



1. Speerschneidera euploca. Thallus much branched, 

 lobes slender, of uniform width and somewhat ascend- 

 ing, gray. Apothecia cup-shaped, sessile. Disk light- 

 brown. Spores typical. 



This is the only species reported from the United 

 States, it is southern in its range. The specimens 

 which came to my notice were associated with species 

 of Collema. It is a small plant, but has a very char- 

 acteristic appearance. 



6. Parmelia. 



It is highly probable that this genus is phylogeneti- 

 cally derived from Lecanora^ as seems evident from a 

 comparison of the higher Lecanoras and the lower 

 ParmeJias. The exact relationship of the Hcematom- 

 mas, Acarosporas and Sj^eerschneidera is not known. 



The thallus of the Parmelias is foliose, large, dis- 

 tinctly branched and lobed. It is held to tlie substra- 



