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 mclude 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 ctherwise with the illustrations. The onus of 
the work has been lessened in no small degree by the interest and en- 
couragement of our colleagues. Tue AUTHORS. 
BERKELEY, CALIFORNIA, 
Feb, 18, 1918. 
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