PREFACE 



IN the preparation of this text and reference book, 'the 

 writer has attempted to consider both the student and 

 the general reader, interested alike in the fundamental 

 requirements of plants and in plant production. Through- 

 out biological study at the present time increased emphasis 

 is placed on the activities and responses of organisms. 

 It is instruction in this type of biological phenomena that 

 is rapidly becoming a part of the cultural side of education, 

 and. the practical value of such knowledge is every day 

 being demonstrated, notably in agriculture and medicine. 

 Plant physiology finds its practical application in plant 

 production, to which it stands in much the same relation 

 as does industrial chemistry to general manufacturing. 



It is somewhat strange, therefore, to find that as a sepa- 

 rate course plant physiology is not yet offered in some of 

 the colleges whose purpose is primarily to train persons 

 for practical or rural pursuits. Such students require some 

 fundamental work, and few will become specialists. For 

 this general class of students, and for other readers as well, 

 there seems to be needed a text (1) that shall exhibit a con- 

 siderable range of material, rather than a few topics ex- 

 haustively treated; (2) that shall include both qualitative 

 and quantitative work; and (3) that shall keep in view, 

 as far as possible, the relations of the science to plant 

 production, drawing the illustrations, wherever convenient, 



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