60 CKREAL RUSTS OF THE UNITED STATES. 



article in Zeitschrift fur Pflanzenkranlcheiten {23, pp. 141-14:4). How- 

 ever, in many cases wliere one rust is always present the differences 

 noted in resistance of the same variety to different rusts may be, in 

 great part, more apparent than real. If one rust attacks certain vari- 

 eties severelj'', another one, the conditions being the same, will natu- 

 rally work most on those varieties where there is least comi^etition, 

 while if the former rust were not present at all or present only in 

 small quantities the latter might affect other varieties as much. 



Damage. — The damage to wheat from this rust has, perhaps, been 

 sufficiently discussed already under orange leaf rust of wheat, hence 

 suffice it to repeat here that it is the destructive wheat rust of the 

 United States. The damaging effects of this rust in Kentucky are 

 shown in tig. I. Such effects seem to be of common occurrence in the 

 State., 



BLACK STEM KUST OF RYE. 



{Piiccinia graminis secalis Eriks. and Henn.). 



It has not yet been determined whether there is a distinct form of 

 P, graminis on rye in this country.^ True, there are in different herba- 

 riums in the United States various sj)ecimens of rust on rye collected 

 here and labeled P. graminis, but many of these identifications are 

 known to be wrong, and as the writer has no practical experience with 

 such a rust either in the greenhouse or in the field, he can as yet make 

 no definite statements in regard to it. In a few experiments, however, 

 he made successful infections on rye and barley, but not on wheat, 

 with what seemed to be uredospores of P. graminis from Hordenm 

 juhatum. These experiments, as already mentioned, seem to show that 

 H.juhaium supports two distinct forms of P. </rrtmi«iv, but there is yet 

 quite a possibility of error because the number of experiments was 

 small. 



BLACK STEM RUST OF OATS. 



{Puccinia graminis aveme Eriks. and Henn.). 



Phys'ological relations. — The apparent differences between this rust 

 and the form on wheat have already been discussed. Besides these 

 differences it has occasionally been seen in cases of adjoining fields of 

 wheat and of oats that one of the cereals was affected with the stem 

 rust while the other remained entirely free from it. Tlie writer has 

 made more inoculation experiments with this rust than with any other, 

 the work having been inaugurated about the same time as that with 

 P. coronata. The results of the experiments are presented in the fol- 

 lowing table: 



' Further observations and facts that have fome to hand very recently make it 

 certain tliat hhick stem rnst occurs on rye, hut whether it is identical with the form 

 on wheat and barley is yet to be determined. 



