15 



parent to offspring? The author then shows the distinction be- 

 tween mheritance and expression of heredity, and passes on to 

 chapter 5, the experimental study of heredity. About half of this 

 is devoted to an exposition of the well known work of Mendel 

 and the rest to the work of Johannsen and Weismann, including 

 a statement of the general unsolved problems developed as a re- 

 sult of their investigations. 



Chapters 6 and 7 discuss the general nature of evolution, which 

 IS regarded as the major problem of botany, describing the ideas 

 of Agassiz and Lamarck briefly and those of Darwin and Wallace 

 in greater detail. These two chapters impress the reviewer as 

 unusually well written. Chapter 8, on experimental evolution, is 

 devoted almost entirely to a summary of the methods and results 

 of De Vries' experiments and to the mutation theory in general 

 The second half of the book deals with the results of evolution 

 ni plants, attempting to present modern ideas on the genetic rela- 

 tions of plants and on the phylogeny of angiosperms in particular, 

 utilizing evidence from the comparative morphology and life his- 

 tory of living plants, from geographical distribution, and from 

 the structure and chronological succession of fossil forms. The 

 author inchnes strongly toward Bower's ideas, but tries to pre- 

 sent all sides of the question impartially. The 44 pages devoted 

 to geographical distribution make an excellent compendium of 

 the whole subject, presenting not the actual facts of modern dis- 

 tribution but rather the general nature and dynamics of the sub- 

 ject, basing the whole on the migration of seeds and proceeding 

 to a discussion of endemism, discontinuous distribution, and the 

 age and area hypothesis. 



A shorter chapter deals with some of the general principles 

 derived from a study of fossil plants, beginning with the condi- 

 tions of fossil formation, presenting a general statement of the 

 distribution of plants in time, and discussing in interesting fashion 

 the causes of the extinction of species. 



In chapter 12 the fossil seed-bearing ferns are discussed in 

 more detail, particularly the Cycadeoidea, which are accepted by 

 the author as the immediate progenitors of angiosperms, follow- 

 ing the views of Arber and others, which are presented in inter- 



