164 THE PLANT WORLD 



that ontogeny repeats phylogeny, Diels condemns this in no 

 uncertain terms, he declaring that it can satisfy but the needs 

 of the imagination. The rev^iewer cannot refrain from re- 

 markmg that while this seems to be the place to which many, 

 especially physiological investigators, would now relegate 

 this theory, yet it is possible that all the facts concerning it 

 are not being taken into account. If the theory is not true, at 

 least in part, i. e. if certain structures and stages occurring in 

 the development of the ulant do not clearly indicate ancestral 

 structures and relations, the bulk of modern morphological 

 theory must fall to pieces. 



While there is not much essentially new in the book, the 

 author has gathered together a large amount of very sug- 

 gestive material and has presented it with unusual clearness 

 and balance. 



jr. B. M. 



