142 BERRY— LOWER EOCENE FLORA OF [Ap"i 25, 



learn to recognize most arborescent forms by their habit and foHage 

 but to most botanists, systematic or otherwise, anything beyond the 

 floral structure receives but scant attention. 



It is reasonable to conclude that palms and tree-ferns were never 

 boreal plants that have in the course of ages become restricted to the 

 tropics as Naumayr once suggested in an efifort to explain their pres- 

 ence within the Arctic circle on other than climatic grounds. Uni- 

 formity of conditions is the foundation upon which the whole fabric 

 of our knowledge of past events rests and it is just as unscientific to 

 assume that the carrying power of water was not conditioned by its 

 velocity during the Tertiary as it is to assume that insolation, humid- 

 ity, rainfall, winds and all the other factors that constituted the en- 

 vironment of the vegetation, had effects different in kind from their 

 effects on the living flora. 



In a study of this sort the chief emphasis should be based upon 

 comparisons with the existing relatives of the fossil forms and not 

 upon a search among the illustrations of works devoted to the study 

 of previously described fomis, often from remote regions, for what 

 appears similar. The latter should not be neglected however and no 

 descriptions are complete unless they include a discussion of the re- 

 semblances and differences of previously described forms that show 

 similarities to the form in hand with their geologic and geographic 

 destribution. Even the most trivial characters of the fossil should be 

 carefully noted since all are or will become valuable in future studies. 

 The living representatives, their habitat, range and variation are of 

 the greatest importance in determining paleoecology. 



Unless there is clear evidence of transportation it may be assumed 

 that strand plants and upland plants will not be found in association 

 and if such seems to be the case, additional study may reveal the 

 errors of determination. 



That all floras are dynamic and not static : that all their elements 

 are more or less plastic in their reactions to the infinite complexity of 

 their environment raises a certain amount of scepticism regarding the 

 methods and results of what may be called paleoecology. This is 

 especially true since so little is known regarding the precise relations 

 between existing plants and their environment. At the same time 

 there is no other method available and it must be considered to be a 



