XVII.] EVOLUTION OF THE FLOWER SEASONS. 289 



if we shall assume that all life -events are determined 

 directly by climatal environment. There are some who 

 look for an explanation of these characteristic periods 

 chiefly in the phylogeny or evolution of the species 

 themselves, rather than in the immediate environment. 

 This view has been forcibly presented by Clarke,* 

 who concludes that early blooming of plants is asso- 

 ciated with the lower, simpler and more generalized 

 species, whilst the later bloom -periods pertain to spe- 

 cies of later or higher developments or to type groups 

 or specialized forms of the lower classes. "In their 

 blooming season, the more perfect succeed the more 

 simple ; the aberrant, the normal ; the specialized, the 

 generalized." There is certainly a strong argument 

 for this position ; but the question now recurs as to 

 why this remarkable correlation exists. Why should 

 the lower or earlier plants have taken to themselves 

 the early season, and the higher or specialized forms 

 to the later season? Mr. Clarke suggests that it is 

 an adaptation to climatic conditions. He assumes that 

 there may have been a constant tendency for plants 

 to bloom earlier, and "the most simple and generalized 

 forms, coming first in the course of floral evolution, 

 have had the longest time in which to adapt themselves 

 to existent climatic conditions ; and, reciprocally, cli- 

 matic conditions have become more and more favorable 

 to the rapid development of the said forms. So a 

 floral type that ages ago would have reached its per- 

 fection only after a long continuance of favoring 

 season, now may burst into the fullness of its maturity 

 with the first warmth of spring. * * * * Thus, 



*Henry L. Clarke, "The Philosophy of the Flower Seasons," Amer. Nat. 

 xxvii. 769 (Sep. 1893). 

 19 SUE. 



