16 A STUDY IN CEREAL RUSTS 



appearance of inoculated plants would lead one to believe that the rusl 

 transfers with greater ease than it really does. Out of a total of 55 

 leaves inoculated only 3 produced pustules. These pustules, although 

 small, were very distinct. Of the remaining leaves, 13 were clearlv 

 flecked. It is the appearance of these so-called flecked leaves which is 

 often misleading. When looking at them from a distance they some- 

 times appear to be quite badly rusted. Closer examination, however, 

 shows that there are no pustules. Sometimes the flecks are so distinct 

 as to suggest the appearance of unruptured pustules. 



The effect of high fertilization 



A rich loam was well mixed with rich barnyard manure. Rye 

 was planted in two pots and the leaves inoculated in the usual manner. 

 Evidences of infection appeared at the usual time. It was found thai 

 the severity of infection was much greater than that on plants grown 

 in unfertilized soil. Of a total of 18 leaves 9 developed pustules and 

 the other 9 were distinctly flecked. The areas of infection on these 

 plants were much larger than on those grown in ordinary soil. The 

 leaf tissues were very clearly killed, sometimes in areas a centimeter 

 long, and in these areas small pustules appeared. The appearance 

 was very characteristic of semi-normal infection. The mycelium spread 

 fairly well, but the host cells were killed and only small pustules were 

 developed. 



The effect of anesthetics 



Plants were inoculated after exposure to ether, chloroform, and 

 nitrous oxide for periods ranging in different experiments from 5 to 

 15 minutes. The difference between the check plants and those ex- 

 posed to anesthetics for 10 minutes was fairly distinct. This was not 

 apparent so much in the number of pustules or flecks, but rather in the 

 sharpness of the flecks. The following were the results : 



After exposure to ether -g^-; 26 flecked 

 After exposure to chloroform -^; 13 flecked 

 After exposure to nitrous oxide -^-5-; 6 flecked 



It will thus be observed that in point of numbers the difference 

 between the success of these infections and those on the check plants 

 was not great. However, a real difference in severity of infection, 

 although not remarkable, did exist. On the other hand the plants in 

 highly fertilized soil developed a larger number of pustules and also a 

 more typical infection. 



Effect of leaf injury 



A number of leaves were injured, just previous to inoculation, by 

 being punctured in many places with a sterilized needle point. Spores 

 were then placed on this injured area in larsfe numbers. The epidermis 



