BOOKS AND CURRENT LITERATURE 



77 



we learn that, amonjj; other factors, the water requirement is influenced 

 by the use of fertilizers, by the limitation of available soil, by soil type 

 which is associated with the food supply, b\' atmospheric conditions, 

 and by parasites. It is greater in dry than in moist air. 



Although not definitely stated it appears that the type of develop- 

 ment sought was that normal for the species. The crops of the experi- 

 ment were "harvested at the stage when similar crops were harvested 

 in the field." Thus, whatever care may be taken with the phj'^sical 

 side of the research there perforce remains much that is inexact, because 

 one is dealing with living plants which vary among themselves not only 

 as species, but also as individuals. Not to be captious, it maj^ be sug- 

 gested that it is hardly just to compare the grain stage of the wheat 

 A\dth the flowering stage of alfalfa, for example, as regards the water 

 reciuirement. It is well knoAVTi that the physiological activities as a 

 whole of a plant at the time of flowering are relatively great, so that it 

 is possible that, if determined at this period, the water requirement 

 might be quite different than if the determination were made at a later 

 period. In this coimection, however, it is recalled that the end sought 

 by the experiments was an economic one primarily, and that, conse- 

 quently, it is the flowering condition of the alfalfa, and the ripened 

 wheat, that are the centers of interest. 



Taking the results as tabulated by the authors we find that the water 

 requirement of the races and species studied, when compared to wheat 

 as unity, is very unlike. For example, alfalfa is 2.11, and millet is 

 0.54, which are the extremes of the series. The actual figures show that 

 millet, as a crop, uses 275 times as much water as the dry material pro- 

 duced, and that alfalfa uses 1068 times as much water as the dry ma- 

 terial produced. The immediate purpose of this note is to institute a 

 similar comparison, using the data of Briggs and Shantz,with two of the 

 Avild species as unity, with whose water requirement that of the cultivated 

 species will be compared. The details of the comparisons are given 

 in the following tables. 



Water requirement of Artemesia frigida 



Artemesia frigida 1.0 



Millet .35 



Sorghum 0.4 



Wheat .66 



Barley 0.7 



Oats .8 



Peas 1 .04 



Alfalfa 1 .39 



