Weaver: effects of rusts upon tkanspiration 



391 



wheat plants consisting of eleven control and 14 diseased plants in- 

 fected with Puccinia graminis tritici. The experiment was contin- 

 ued until March 16, a period of nine days. The results are shown 

 graphically in figure 4. Here again the heavy lines represent the 

 diseased plants and the light lines the controls. The apparent low 

 loss of water of these plants during the first period is due in part 

 to the shorter interval between weighings (here 24 hours) and in 



Fig. 5. Graphs showing the relative transpiration of healthy and rust-infected rye. 

 The broken line shows the evaporating power of the air as measured 

 by porous cup atmometers. 



part to the fact that after removing the plants from the moist atmo- 

 sphere of the inoculating chamber it was expedient to keep them in 

 a fairly humid place for a time. 



The pustules began to appear on March 11 and by the 13th were 

 quite abundant, except on the plants indicated by the lowest heavy 

 line, where for some reason their appearance was delayed until 

 about the 13th. 



A striking relationship between increased transpiration and 



