viii Preface by the Author 



summer of 1904, and these lectures are offered in this 

 form to a public now thoroughly interested in the pro- 

 gress of modern ideas on evolution. Some of my experi- 

 ments and pedigree-cultures are described here in a man- 

 ner similar to that used in the " Mutationstheorie," but 

 partly abridged and partly elaborated, in order to give a 

 clear conception of their extent and scope. New experi- 

 ments and observations have been added, and a wider 

 choice of the material afforded by the more recent cur- 

 rent literature has been made in the interest of a clear 

 representation of the leading ideas, leaving the exact and 

 detailed proofs thereof to the students of the larger book. 



Scientific demonstration is often long and encumbered 

 with difficult points of minor importance. In these lec- 

 tures I have tried to devote attention to the more im- 

 portant phases of the subject and have avoided the de- 

 tails of lesser interest to the general reader. 



Considerable care has been bestowed upon the indica- 

 tion of the lacunae in our knowledge of the subject and 

 the methods by which they may be filled. Many inter- 

 esting observations bearing upon the little knovm parts 

 of the subject may be made with limited facilities, either 

 in the garden or upon the wild flora. Accuracy and per- 

 severance, and a warm love for Nature's children are 

 here the chief requirements in such investigations. 



In his admirable treatise on Evolution and Adaptation 

 (New York, Macmillan & Co., 1903), Thomas Hunt Mor- 

 gan has dealt in a critical manner with many of the 

 speculations upon problems subsidiary to the theory of 

 descent, in so convincing and complete a manner, that I 

 think myself justified in neglecting these questions here. 

 His book gives an accurate survey of them all, and is 

 easily understood by the general reader. 



In concluding I have to offer my thanks to Dr. D. T. 

 MacDougal and Miss A. M. Vail of the New York Botan- 

 ical Garden for their painstaking work in the prepara- 

 tion of the manuscript for the press. Dr. MacDougal, by 



