THE EFFECTS ОЕ SURFACE FILMS ОХ THE RATE OF 
TRANSPIRATION: EXPERIMENTS WITH POTTED 
POTATOES 
B. M. DUGGAR 
Physiologist to the Missouri Botanical Garden, in Charge of Graduate Laboratory 
Professor of Plant Physiology in the Henry Shaw School of Botany of 
Washington | University 
AND J. S. COOLEY 
Formerly Rufus J. Lackland Fellow in the Henry Shaw School of Botany of 
Washington University 
In a previous report! we have presented data which is be- 
lieved to justify the conclusion that an application of a surface 
film of Bordeaux mixture to the leaves of the castor bean or 
the tomato increases materially the rate of transpiration. The 
importance of a careful determination of various physiological 
effects of this spray mixture was suggested primarily by the 
increased vitality and yield exhibited by potatoes (Solanum 
tuberosum) treated with this fungicide during seasons when 
fungi and insects were unimportant factors. In our previous 
experiments the potato was not included, and it seemed most 
important, as a next step, to ascertain the effects of certain 
sprays upon the transpiration of this plant. 
Experience has demonstrated that the potato may not be 
used satisfactorily in potometer experiments. Moreover, it 
was desired to arrange the experiment so that the transpiration 
quantities obtained might represent an interval of a week or 
more. On the other hand, it had been found as a result of our 
previous work with potted tomatoes that a very considerable 
amount of labor is required when it becomes necessary to add 
measured quantities of water every day to a series of fifty or 
more potted plants. Accordingly, for this and for other work 
proposed, a method was devised whereby we were able to employ 
a self-watering device based on a principle often used in the 
laboratory. 
1 Duggar, B. M., and Cooley, J. S. The effect of surface films and dusts on the 
rate of transpiration. Ann. Mo. Bot. Gard. 1:1-22. pl. 1. 1914. 
ANN. Mo. Вот. Garp., Vor. 1, 1914 (351) 
