20 A STUDY IN CEREAL RUSTS 



The rust can be transferred successfully from oats to any one of 

 the other cereals. It infects rye much more easily than wheat or bar- 

 ley. Anesthetics help to break down the barriers as does a high degree 

 of soil fertilization. It should be mentioned that this fact seems due, 

 not to any new ability the rust fungus has of attacking an uncongenial 

 host, but to an increased capacity for development. Here again evi- 

 dence of the possible nature of resistance is offered by the inoculated 

 plants. The flecks, whether large or small, consist in many cases of 

 dead tissue of the host plant. Histological examination shows that the 

 fungus gains entrance but cannot develop to any extent in these areas 

 which are killed by the fungus itself. 



EXPERIMENTS WITH PUCCINIA GRAMINIS SECALIS 

 These experiments were not very extensive and were made with 

 the idea of determining rather the character than the number of suc- 

 cessful infections. 



INOCULATIONS ON WHEAT 



In all 70 leaves were inoculated. None of them produced pustules, 

 but 18 became flecked. The flecks were distinct but in no case were 

 they large. There seemed to be much less dead tissue than is the case 

 in many of the other forms, as for instance rye inoculated with barley 

 rust. In fact the flecks were hardly noticeable unless one looked very 

 carefully for them. Apparently they were due to the death of host- 

 plant cells in the inoculated area. 



INOCULATIONS ON OATS 



In addition to a small number of control inoculations, some were 

 made after exposure to ether and others after exposure to chloroform. 

 The anesthetics apparently made no particular difference in the suc- 

 cess of the attempts, although there were more flecked leaves after ex- 

 posure to chloroform. Nothing out of the ordinary appeared so only 

 the summaries are given : 



After chloroform, 5 min. T ^-; 5 slightly flecked 

 After ether, 5 min. -^ ; 2 slightly flecked 

 Under ordinary conditions -^; 1 slightly flecked 



INOCULATIONS ON BARLEY 



After exposure to ether for 5 minutes, 16 out of 21 inoculated, 

 leaves became very distinctly flecked. There were many of these 

 flecks all along the line of inoculation. They were very suggestive of 

 the flecking in other forms in which the mycelium was known to have 

 spread to some extent. However, no pustules were developed. Judg- 

 ing from the experience with other forms, if these plants had been 

 highly fertilized they might have developed pustules. Of the check 



