PREFACE 



Of all the sciences that contribute to the great, tertiary composite 

 which is known as agriculture none is more important economically than 

 genetics. One may not overlook the fundamental relation borne by the 

 primary sciences, mathematics, physics and chemistry, and by the second- 

 ary sciences, botany, zoology, geology, meteorology and economics, to 

 the production and distribution of raw materials. But we confidently 

 assert that the science which underlies the improvement of plants and 

 animals for agricultural purposes is destined to receive increasing atten- 

 tion in agricultural education and in agricultural practice. Without 

 doubt vast possibilities await realization through the more thorough and 

 systematic development of our living economic resources. Such de- 

 velopment is directly dependent upon the successful utilization of genetic 

 principles in plant and animal breeding. The science of genetics is still 

 very young, but it is firmly established and is developing rapidly. It 

 claims the attention of the producer of today and invites the most serious 

 study of the agriculturist of tomorrow. It lays claim also to the interest 

 of the eugenist, the sociologist and the philanthropist and all students 

 of biology. 



This text has been prepared in response to a real and widely recognized 

 need. The experience of the authors in teaching the principles of breed- 

 ing to undergraduate students has forced home the conviction that an 

 adequate presentation in a single text of the facts and principles of 

 genetics and their practical applications is a prime necessity. Those 

 familiar with the literature of the subject will appreciate the magnitude 

 of the task and, we trust, will be lenient in criticizing our choice of 

 subject matter. It is impossible to include many things of mutual 

 interest to genetics and agriculture if the work be limited to a single 

 volume. We are keenly aware of many deficiencies and it is our desire 

 to prepare a revised edition of the book in the near future. With this 

 in view the suggestions of others are earnestly solicited. 



We take this opportunity to express gratitude to all who have rendered 

 assistance, especially to those who have read portions of the manu- 

 script or assisted in proof-reading and to all who donated or loaned photo- 

 graphs or who assisted otherwise with the illustrations. The onus of 

 the work has been lessened in no small degree by the interest and en- 

 couragement of our colleagues. THE AUTHORS. 



BERKELEY, CALIFORNIA, 

 Feb. 18, 1918. 



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