Aug. 27. 1917 Puccinia graminis on Cereals and Grasses 



461 



a distinct biologic form, although it is somewhat different from any 

 other form studied. 



Table XXVII. — Results of inoculations with urediniospores from Triticum vulgare 



a One generation on club wheat in greenhouse before inoculations were made. 

 b Normal infection. 



In the Palouse country of Washington and Idaho there is a common 

 form resembling P. graminis tritici in many respects, but still very 

 distinct from it. There seems sufficient reason for considering this a 

 distinct biologic form for which the name 'Puccinia graminis tritici 

 compacii" is suggested. 



Except for the variations mentioned, all of the rusts collected could 

 be referred to one of the ordinary biologic forms, although there were 

 sometimes slight differences in \'irulence. In general, however, the 

 results of inoculations with different strains of a biologic form were 

 monotonously uniform. 



The results show very clearly, however, that the forms of stemrust 

 which attack cereals commonly occur on many wild grasses over a 

 large area. 



After the identity of the different strains of biologic forms isolated 

 from grasses or cereals from the field had been established inoculations 

 were made on cereals and grasses, in order to determine whether the 

 behavior was always constant. 



KEY TO TABIvES XXVIII-XXXIII 



In Table XXVIII, and those following, "Original host" refers to the 

 host on which the rust was collected in the field; "Immediate host" 

 refers to the host from which spores were taken for inoculation; "Trials" 

 refers to the number of different sets of inoculations made, plus ( + ) 

 indicating the number of trials in which some plants became infected 

 and minus ( — ) the number of entirely unsuccessful trials. The results 

 are given in the form of a fraction, the denominator denoting the total 

 number of leaves inoculated in all trials and the numerator the number 

 which became infected. 

 100305°— 17 3 



