Aug. 27, 1917 Puccinia graminis on Cereals and Grasses 



437 



Table IV. — Results of inoculations with urediniospores from Agropyron smithii Rydb. 



From the rusted wheat 18 successive transfers were made during a 

 period of 10 months, 17 of which were to barley Only about one-half 

 of the total number are shown in the diagram; the other results were 

 similar to those shown here. Wheat and barley were easily and heavily 

 infected when inoculated, while rye and Agropyron repens were weakly 

 infected. The uredinia of P. graminis triiici on rye are very small and 

 are usually surrounded by dead areas, thus being easily distinguishable 

 from those of P. graminis secalis. The uredinia of P. graminis tritici on 

 A. repens are as a rule very small, although there seems to be considerable 

 variation. Whether this is on account of the condition of the seedlings 

 or the conditions for infection is still doubtful. It is quite clear from 

 the behavior of the rust that this form was P. graminis tritici. 



The reason why only 12 of the 16 leaves of wheat inoculated with 

 the rust from Agropyron repens developed uredinia, whereas 100 per cent 

 of the leaves became infected in the subsequent set of inoculations, is 

 that the uredinia on A. repens were very small, thus necessitating light 

 inoculation. Four of the wheat leaves therefore escaped infection. Those 



