170 GUIDE TO THE STUDY OF LICHENS. 



1. Trypethelium. 



The thallus is hypophloedal during its entire existence. 

 It consists simply of a deficient network of hyphse en- 

 closing a few algae (^Chroolepus). The bark over the 

 apothecia and thallus is smooth and of a rusty-red 

 color which gradually fades into brownish or green- 

 ish. 



The apothecia are likewise hypophloeodol, and occur 

 in clusters of from five to forty. Each apothecium is, 

 however, independent of its neighbors, and may be 

 considered as an individual of the colony. As the 

 apothecia grow, they push up the superimposed bark 

 mi til it forms a more or less irregular elevation. The 

 spores escape through minute apical pores. 



The spores are normally colorless and eight-celled, 

 spindle-shaped ; the plasmic masses diamond-shaped. 



The genus is essentially southern. The representa- 

 tives occur upon trees. Some authors combine it with 

 Pyrenula. 



li Trypethelium virens. Bark above thallus smooth, 

 light-brown to pale-green. Apothecial colonies con- 

 sist of from ten to forty minute apothecia. Perithe- 

 cium black. Spores colorless, six to eight-celled, 

 42/x X 10/x. 



Bark is tinged reddish or rusty brown, over and 

 about the apothecia. Nearly all of the so-called 

 species of Trypethelium require further study. 



2. Pyrenula. 



This is another lowly-organized lichen-genus. The 

 thallus as well as the apothecia are hypophloeodal, and 



