BIOLOGIC FORMS 15 



SUMMARY OF INOCULATIONS WITH PUCCINIA GRAMINIS HORDEI 



Wheat and barley are not included since in nearly every case 100 

 per cent of infection results. The denominator in each case represents 

 the total number of leaves inoculated, and the numerator, the number 

 of leaves which developed pustules. 

 Barley rust to: 



Oats T $ T ; 8 slightly flecked 



Oats after exposure to ether o . JEJ fl ec ked 



Oats after exposure to chloroform -- ; 8 flecked 

 RyeJ-1; 29 ver y stron gly flecked 



It will thus be seen that barley rust does not find either rye or oats 

 a congenial host. It was transferred to rye much more easily in these 

 experiments than in those reported by other investigators in this coun- 

 try. Without exposing the host plants to anesthetics, however, no suc- 

 cessful infection of oats was obtained. By the use of ether and chloro- 

 form the possibility of infection was somewhat increased, as evidenced 

 by the formation of pustules on a small percentage of leaves and the 

 increased percentage of flecked leaves. In addition to this, the flecks 

 were much more distinct than those on the check plants. 



EXPERIMENTS WITH PUCCINIA GRAMINIS AVENAE 



GENERAL STATEMENT 



This rust in this country is supposed to infect no cereal except 

 oats, although it is capable of infecting a number of grasses. Carleton 

 (1899, p. 60) was unable to transfer it successfully to wheat, barley, 

 or rye. Eriksson (1902, p. 601) mentions it as being found on oats 

 and 18 species of grasses in Sweden. Freeman and Johnson (1911, 

 p. 22), however, find that it can be transferred to barley also, and they 

 report that Derr succeeded in obtaining direct transfers from oats to 

 wheat and rye. 



INOCULATIONS ON RYE 



Since Derr, according to Freeman and Johnson (1911, p. 22), 

 obtained but one successful infection by inoculating rye with stem 

 rust of oats, a large number of trials were made with this form, espe- 

 cially since the same authors (I.e. p. 23) assert that under favorable 

 conditions these can undoubtedly be made. 



Inoculations under ordinary conditions 



The results of inoculations made under average conditions show 

 clearly that it is possible to transfer the rust from oats to rye. Al- 

 though the percentage of entirely successful infections^was small, the 



