EFFECT OF BOKDEAUX MIXTURE ON TRANSPIRATION 85 



in which the plants were rooted was very much greater on this 

 day than was the case on either of the other two days. 



The graphs here presented possess all the characteristics of 

 the t^Tpical graphs of foliar transpiring power thus far pub- 

 lished, and in addition to this, they bring out very clearly the 

 influence of a surface film of Bordeaux mixture upon the trans- 

 piring power of the leaves of the tomato plants here employed, 

 for the particular sets of conditions under which the tests were 

 made. Whatever may be the nature of the influence of a film 

 of Bordeaux mixture, effective in producing higher indices of 

 transpiring power, it is clear that this influence is just as effec- 

 tive to increase and to maintain these indices when their values 

 are low as it is when their values are high. 



It should be stated that the data here presented involve the 

 tests of comparatively few of the total number of leaves of a 

 single plant. As has already been pointed out, the leaves chosen 

 from each plant for these tests were neither very old nor verj' 

 young, and may, therefore, be considered to be representative 

 of the leaves of the plant as a whole. Had it been practicable 

 to make simultaneous tests, similar to these, upon a large num- 

 ber of leaves at various stages of growth and maturity, or upon 

 all the leaves of each plant here employed, it is questionable 

 whether the average data thus obtained would show the results 

 to be essentially different from those here presented. 



It was not the purpose here to inquire into the causes under- 

 lying the modification of the indices of transpiring power through 

 the agency of Bordeaux mixture, but merely to determine the 

 effect of surface films of this spray material on the transpiring 

 power of tomato plants under cultivation in the open field, by 

 the improved method of standardized hygrometric paper. 



SUMMARY 



The results obtained from these tests demonstrate clearly 

 enough that the method here employed furnishes an adequate 

 and simple means of studying the transpiring power of plants 

 which have been treated with surface films of Bordeaux mixture. 



