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MINNESOTA BOTANICAL STUDIES 



to November 23. Here again the results in all cases gave a higher 

 transpiration rate for diseased plants. Since they merely confirm 

 the evidence already given they need not be included. 



Experiments with Oats 



An experiment with White Russian oats, rusted with Puccinia 

 graminis avenae, was carried out from January 16 to the 23rd. 

 Eight diseased and nine control plants, making a battery of eight 

 containers, were used. During nearly the entire period conditions 

 for transpiration were unfavorable. The results are shown in figure 

 7. The rust pustules began to appear on January 20 and were well 

 out by the 22nd. The rusted area was not measured as in the fore- 

 going experiments, but a careful count of the number and meas- 

 urements of the average size of rust pustules gave a total pustular 

 area of 0.5 per cent. It may be noted that while the relative trans- 

 piration was low, the increase of the rusted over the healthy plants 

 was, during the last interval, 37 per cent. 



Earlier experiments with oats were conducted for shorter inter- 

 vals of time and just after the rust pustules had appeared. A part 

 of these data are recorded in table I. In these experiments the 

 amount of rust ranged from a light to a very heavy infection, but 

 the exact amount was not determined. 



table I 



*ln this experiment the rust used was Puccinia coronata. 



