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REVIEWS 



Gagrer's Heredity and Evolution in Plants 



Under this comprehensive title, Dr. C. Stuart Gager has re- 

 cently published a little book (P. Blakiston's Son & Co., pages 

 xiii + 265, price $1.25) of remarkable interest: remarkable in 

 that it presents within so small a compass a digest of such broad 

 and complex subjects. 



The whole book may be siunmarized in a few lines. The re- 

 productive system is the machinery for heredity ; long-continued 

 heredity is evolution ; the results of evolution are expressed by 

 the morphological differentiation of plants and by their distribu- 

 tion in space and time. Each of these themes is discussed by the 

 author in turn. 



Under the first head, the author devotes two chapters to the 

 life history of a fern, wisely selecting for illustration a plant with 

 well developed gametophyte rather than an angiosperm. The 

 third chapter introduces some general considerations based on 

 the facts presented in the two preceding, and discusses briefly but 

 clearly the general nature of reproduction, alternation of genera- 

 tions, and reduction ; this is followed by a general definition of 

 inheritance and an entirely too brief discussion of the struggle 

 for existence and the elimination of the unfit. Unfortunately 

 this portion is marred by two rather serious errors or omissions. 



The fourth chapter deals with the laws of heredity. Here the 

 reviewer, who makes no pretence of erudition in genetics, at 

 once came into difficulties. On page 40, inheritance is defined as 

 " the recurrence in successive generations of a similar cellular 

 constitution," while on page 48 the statement is made that in- 

 heritance is " all that an organism has to start with. It is the 

 protoplasmic substance, with all its potentialities, passed on from 

 parent to offspring." Now thorns recur on successive genera- 

 tions of roses, agreeing with the first definition, but a young rose 

 does not have thorns to start with. Would it not have been just 

 as clear to the general reader if inheritance had been defined as 

 the potentiality of the protoplasmic substance passed on from 



