﻿208 BOTANICAL GAZETTE [march 



gave way to a large extent to conifers, especially pines and 

 cedars. In addition to the ecologic factors already noted, it may 

 be said that protection from wind is a factor aiding in the devel- 

 opment of the Cladonia rangifcrbia formations, as the plants of 

 such societies can hardly endure the effects of strong winds. 



It may be readily inferred from certain statements in this 

 paper that it is by no means the intention to convey the impres- 

 sion that the Cladonia lichen societies are the only ones to be 

 found upon tali. Other talus lichen communities, though not so 

 striking in appearance, would doubtless prove to be quite as 

 interesting if studied in detail. Such lichen societies as have 

 been considered in the present paper doubtless occur in various 

 portions of North America, especially in mountainous regions, 

 and comparative studies as to ecologic conditions, adaptations, 

 and species contained in the formations in various portions of 

 our territory would be both interesting and instructive. 



Upper 1o\ya University, 



Fayette, Iowa. 



