Weaver: effects of rusts upon transpiration 



395 



From these data it is evident that these rusts on oats not only 

 increased transpiration in all cases but that in some instances the 

 increase amounted to several times that of the normal water loss. 



Experiments with Barley 



The following experiments, which are illustrative of others con- 

 ducted with Odessa barley rusted with Puccinia graminis hordei, 

 may be summarized in the table II. The rusted area was not de- 

 termined. 



table II 



Date of the be- 

 ginning of 

 experiment 



Duration 

 in hours 



Condition 

 of plant 



Transpiration in 

 grams per sq. 

 dm. of trans- 

 piring surface 



Percentage of 

 water transpired 



Experiments with Corn 



In this series a yellow dent corn, Minnesota 13, was used. 

 Uredospores of Puccinia Sorghi Schw. were collected from a field 

 in October and the rust was kept growing on stock cultures in the 

 plant house. The experiments with corn were performed before a 

 satisfactory method for determining the pustular area had been 

 devised. An approximation of the rusted area was made by cutting 

 out and weighing the affected parts and comparing this with the 

 total leaf weight. Further studies showed that this gave results 

 quite too high. In these experiments with corn a single plant was 

 grown in a container. In the experiments recorded in table III, 

 plants were inoculated on the first and second leaves as soon as the 



