PREFACE TO THE FIRST EDITION 



The writer of a new book in an old field must give a reason for 

 his work. As a teacher of plant physiology I have felt a need for 

 a teachable text for elementary students. We have some very 

 fine reference books for collateral reading, but a modern text 

 written like a text in other fields is at present not to be found. 

 This book, which has grown out of a series of lectures given at the 

 University of Wisconsin and later at the University of Arizona, 

 is planned to meet the need for a new presentation. 



Let me emphasize that this is a book for students and not for 

 teachers, a textbook and not an exhaustive treatise. I have tried 

 to make a connected story which the student can follow, and 

 although my account may be unliterary I hope that it is readable 

 and comprehensible. 



Plant physiology is largely a combination of elementary botany, 

 physics, and chemistry; and I have therefore assumed that the 

 student has an elementary knowledge of these contributing 

 sciences. Often a problem of plant physiology can be clarified by 

 material from animal or general physiology, and I have not at- 

 tempted to draw the line too sharply between these various phases 

 of physiology. Chapters XII-XV, which are chiefly chemical in 

 nature, are really phases of phytophysiological chemistry but are 

 needed by the student if he is to appreciate the work of the plant 

 as a living factory. 



I have aimed to make the drawings and illustrations as helpful 

 as possible. The photographs of botanists were very kindly sup- 

 plied to me in response to a request which I sent to a number of 

 men, and are of living workers in the field. The student too often 

 gains the impression that he is studying a dead science, which has 

 been developed chiefly by men no longer alive. 



The questions are intended (1) to call attention to matters 

 mentioned in the text which the student might otherwise neglect, 

 (2) to stimulate thought and reflection, and (3) to encourage the 

 student to go to other sources of information. Most of the ques- 

 tions belong in categories (2) and (3). They are not answered 

 in the text at all or only incompletely. They are meant as out- 



ix 



