LETTER OF TRANSMITTAL. 
U. S. Department of Agriculture, 
Bureau of Plant Industry, 
Office of the Chief, 
Washington } B.C., June 16, 1913. 
Sir: I have the honor to transmit herewith a paper entitled "The 
Water Requirement of Plants. II. — A Review of the Literature," by 
Dr. Lyman J. Briggs, Biophysicist in Charge of Biophysical Investi- 
gations, and Dr. H. L. Shantz, Plant Physiologist, Alkali and Drought 
Resistant Plant Investigations. This paper was prepared hi connec- 
tion with their investigations of the water requirement of crop plants 
in the Great Plains and consists of a review of the various measure- 
ments which have been made dealing with the water requirement of 
crops. It is hoped that this paper may prove of value, not only as 
a presentation of the present state of our knowledge regarding the 
amount of water required by crops in the production of a unit weight 
of dry matter, but in indicating as well the lines along which future 
investigations in this subject can be most profitably carried on. 
I have the honor to recommend the publication of this paper as 
Bulletin Xo. 285 of the Bureau series. 
Respectfully. Wm. A. Taylor, 
Chief of Bureau. 
Hon. D. F. Houston. 
Secretary of Agriculture. 
285 q 
