SEVENTH ANNUAL MEETING 



67 



The upper stratum of the oat field also shows considerable 

 variations which correspond more or less to those in the wheat 

 field. 



In order to determine the relation of climatic conditions to 

 crop production the work on soil moisture and evaporation 

 should be extended to deeper strata of soil and to higher strata 

 of the atmosphere. Soil and air temperatures should also be 

 recorded in these extended strata since such temperatures 

 probably are directly effective on plant growth. The amount of 

 precipitation and of irrigation water should also be recorded 

 throughout the year, together with the soil conditions which 

 effect the conservation of the same. The distribution and 

 stages of development of the stem and root systems should be 

 determined from time to time as the crops progress. The 

 osmotic force of the roots of various crops in comparable 

 stages of development may also be of interest in this con- 

 nection. 



The above methods of determination can be profitably ap- 

 plied to any crop at different stages in its development and 

 under different methods of cultivation in order to obtain a 

 quantitative statement of the relative effectiveness of methods 

 of cultivation. 



I wish to acknowledge many helpful suggestions by Doctor 

 George D. Fuller, under whose direction this work has been 

 done. 



TABLE I. 



Wilting Coefficients and Mean Percentage of Growth-Water in 

 Various Associations from June 1 to August 16, 1913 



•Taken from Fuller's data in the same region. 



LITERATURE CITED 



1. Fuller, George D., "Evaporation and Soil Moisture in Relation to the Suc- 

 cession of Plant Association." Bot. Gaz. 58; September, 1914. 



2. Livingston, B. E., "Operation of the Porous-Cup Atmometer." Plant World, 

 13; 111-119, 1910. 



3. Briggs, L. J. and S'chantz, H. L., "The Wilting Coefficient for different 

 Plants and its Indirect Determination." U. S. Dept. of Agr., Bureau of Plant In- 

 dustry, Bui. No. 230, 1912. 



