PREFACE 



Probably no phase of science has ever de\'eloped 

 more rapidly than has the subject of genetics during the 

 last decade. The number of competent investigators 

 has so increased, the scope of investigation has so broad- 

 ened, and the methods have so improved that there exists 

 now an extensive literature on the subject. The rapi(Hty 

 of its publication brings repeated changes in intcrj:)reLa- 

 tion of the phenomena of heredity, and keeps the subject 

 in a state of flux. For this reason it is difficult and per- 

 haps even dangerous to prepare a textbook on genetics. 

 Some of the views expressed in the manuscript may be 

 out of date when the book is issued. It is evident, there- 

 fore, that the material of the present text can represent 

 only one author's interpretation of the status of genetics 

 in 1923. 



Plant Genetics, by John M. Coulter and Merle C. 

 Coulter, was published in 191 8. The present text is 

 more than a new edition of the earher one, since it repre- 

 sents a thorough revision of the material presented. 

 The former title was felt to be an unfortunate one, since 

 it seemed to imply that the genetics of plants is some- 

 thing different from the genetics of animals. Since the 

 fundamental principles of inheritance are the same in the 

 two groups of organisms, and since it is necessar\' to use 

 many of the results of animal investigation to illustrate 

 certain points, it is felt that a more appropriate title 

 for the present text is Outline of Genetics, with Special 

 Reference to Plant Material. 





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