228 



Journal of Agricultural Research 



Vol. XV, No. 4 



Table I. — Results of inoculating cereals with cecios pores of biologic forms of Puccinia 



graminis — Continued 



Barberry probably does not increase the host range of biologic forms 

 commonly. If it did, aeciospores collected in the field ought to infect 

 cereals and grasses more indiscriminately than they do. On the other 

 hand, the biologic specialization in the aecial stage is apparently the same 

 as that in the uredinial stage. The percentage of infected leaves was 

 often low, but this is often true when inoculations are made with aecio- 

 spores. All of the results recorded in Table I, except No. 16, might 

 equally well have been the result of inoculations with urediniospores, 

 except that a larger percentage of inoculated leaves would have been 

 infected. 



The results shown in No. 16 can not be explained, unless accidental 

 infection took place. The grass was collected in the fall and kept until 

 the next July. The barberry had been kept in the greenhouse under a 

 double muslin cage until inoculated and was again covered immediately 

 after removal from the incubating chamber. Three biologic forms 

 developed on the barberry; how they got there can not be stated with 

 certainty. 



EXPERIMENTS WITH CEREALS AND GRASSES AS BRIDGING HOSTS 



Many hosts equally susceptible to P. graminis secalis and P. graminis 

 tritici were used as bridging hosts in attempts to change the parasitism 

 of the two forms. Barley, various species of Elymus, Agropyron, 

 Hordeum, and Bromus were used most. Bromus tectorum was used as 



