Aug. 27, 1917 



Puccinia graminis on Cereals and Grasses 



455 



The work with barley was done particularly to determine whether a 

 special biologic form occurs on barley (Table XXI). Freeman and John- 

 son (14, p. 19) obtained results which led them to believe this to be the 

 case. The form on barley in their experiments seemed to infect rye and oats 

 more readily than either the wheat stemrust form or the rye form. They 

 therefore named the barley form P. graminis hordei F. and J. (14, p. 27). 

 It will be seen from Table XXI that all of the rust collected on barley in 

 the field by the writers was ordinary P. graminis tritici. Only two sets 

 of inoculations were made on oats, but successful infection did not occur 

 in either. However, Derr (14, p. 18) successfully infected oats with 

 P. graminis tritici taken directly from wheat. Freeman and Johnson 

 (14, p. 20) also succeeded in infecting rye more easily with barley rust 

 than with wheat rust. However, the writers obtained, in a number of 

 sets of inoculations, a greater percentage of infection on rye with P. 

 graminis tritici than Freeman and Johnson report having obtained with 

 P. graminis hordei. The percentage of leaves of rye which become 

 infected when inoculated with the same strain of P. graminis tritici and 

 the degree of infection both vary greatly in different trials. 



Further, barley can be infected by all of the common biologic forms of 

 P. graminis, and the possibilities for mixed strains on this host are there- 

 fore not to be overlooked. It is unquestionably a very congenial host 

 for P. graminis secalis, P. graminis tritici, and P. graminis tritici compacti 

 and can be quite consistently weakly infected by P. graminis avenae, P. 

 graminis agrostis, and P. graminis phleipratensis. It is unquestionably 

 the least specialized of any of the cereals toward P. graminis. 



It is doubtful, therefore, whether there is a separate biologic form for 

 barley. 



Table XXII. — Reszdts of inoculations with uredinios pores from Hystrix patula Moench 



Both P. graminis tritici and P. graminis secalis may occur on Hystrix 

 patula (Table XXII). The P. graminis secalis, however, which was 

 isolated from the grass differed somewhat from ordinary strains of this 

 biologic form. The urediniospores are smaller, and the rust is less viru- 

 lent on the cereals than P. graminis secalis. This is especially true of 



