PREFACE 



The present little book was originally intended to be 

 merely a reprint of Chapters XXXI to XXXVIII of the 

 author's Fundamentals of Botany. The reprinting of those 

 chapters was suggested by comments received from various 

 correspondents, who pointed out that the subject matter 

 which they cover had not been elsewhere presented in so 

 concise a treatment in one volume, and in a manner 

 suited, not only to beginning students, but also to more 

 general readers. The chapter on Experimental Evolu- 

 tion has received the approval of the author of the mu- 

 tation theory, as being an accurate presentation of the 

 essentials of that theory. ' I have especially appreci- 

 ated," writes Professor de Vries, "the statement of the 

 difference between fluctuating and saltative variation, 

 which is, to my mind, the real empirical basis for the 

 theory, far more than the experiments on mutation with 

 single plants. The relation of my view to Darwinism 

 is misunderstood by many authors, and it is a great satis- 

 faction to me that you have outlined it in such a plain 

 way." 



In the preparation of the copy for reprinting, consider- 

 able new matter has been added, certain sentences and 

 paragraphs, pertinent only to an elementary text-book, 

 have been omitted, and others recast, and several fresh 

 illustrations have been introduced, either as new or as 

 substitutes. 



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