^.S^^N. 



PREFACE 



Thtse lectures on the Inorganic Nutritum of Plants given at 

 Harvard University, under the Prather Lectureship, were not 

 originally intended for publicatio7u Suggestions were later made 

 that these brief reviews might have an interest for a wider 

 audience. Dr. Vehidoorn was sufficiently impressed by this point 

 of view to undertake publication of the lectures. They have 

 been revised and two s^ipplementary lectures added. 



Obviously, this srjiall volume cannot have any of the char- 

 acteristics of a monograph or of a text. Its purpose is to 

 present a general perspective of several important aspect^s of the 

 field of plant nutrition, with a broad interpretation of this term 

 in mhid. It is hoped that some of the problems of the soil-plant 

 system awaitiiig further exploration may be brought into focus. 



Underlying the plan of these discxLSsions is the thought that 

 some students of the plant sciences, especially among those who 

 are not primarily concerned with the literature of plant nutri- 

 tion, may find it ivorthwhile to gain such impressions of this 

 complex field of study as can be offered in highly compact form. 



Most of the illustrative material is drau~n from the experi- 

 ences of several groups of Calif omian workers. The assumption 

 was made that in lecturer of the present type and objective the 

 writer should emphasize the work with which he has had the 

 most direct contacts. The limited scope of the lectures precluded 

 consideration of a I'ast number of important contributions to the 

 field surveyed. 



I ivish to express my deep appreciation to T. C. Broyer for 

 his assistance in the preparation of the illustrative material and 

 for other assistance. I am also grateful to D. I, Arnon, H, S. 

 Reed, J. C. Martin, and W. P. Kelley for making available 

 certain of the illustrations in original form. 



The Author 



