460 



JoiCrnal of Agricultural Research 



Vol. X, No. 9 



from B. vulgaris was very severe, clearly establishing the identity of the 

 rust. 



Diagram la. — Results of inoculations with aedospores developed on Berberis vulgaris from inoculations 

 with teUospores from Sporobolus crypiandrus (Torr.) Gray. 



(Rye - 



Table XXVI. — Results 0/ inoculations with urediniospores from Triiicum compactum 



Host 



a Old spore material; many spores probably not viable. 

 ^ Hypersensitive. 

 <= Normal infection. 



The low percentage of infection from Triticum compactum is probably 

 due to the fact that inoculations were made about a month after the rust 

 was collected, and many of the spores had very probably lost their 

 viability (Table XXVI). ' 



It is not known whether all of the rust on club wheat west of the 

 Rocky Mountains is of this type, since it is also susceptible to ordinary 

 P. graminis tritici; but, on account of the absence of ordinary P. graminis 

 tritici from grasses on which it would be expected to occur and on account 

 of the prevalence of the club-wheat form on those grasses, it is probable 

 that by far the greatest amount of rust on club wheat west of the moun- 

 tains is P. graminis tritici compacti. 



Only a few inoculations were made directly from wheat. These 

 represent only a very small proportion of the total number of inocula- 

 tions made with P. graminis tritici. Further inoculations were made 

 with the rust, developed as a result of the inoculations reported in 

 Table XXVII, but the results were of no particular interest, since they 

 did not differ from any of those previously obtained. 



It is quite apparent that in the upper Mississippi Valley and northern 

 Great Plains area there are at least five biologic forms of Puccinia grami- 

 nis, if P. phleipratensis be considered a biologic form, which seems 

 quite justifiable — viz, P. graminis tritici, P. graminis secalis, P. graminis 

 avenae, P. graminis agrostis, and P. graminis phleipratensis. In addi- 

 tion to these may be mentioned the strain P. graminis secalis found on 

 Hystrix patula. There is probably not sufficient reason for calling this 



