Nov. 1. 191S Infection Experiments with Timothy Rust 213 



It will thus be seen that the rust from timothy transfers directly to 

 three of the common cereals. Neither Eriksson and Henning (3) nor 

 Johnson (4), as previously mentioned, were able to obtain successful infec- 

 tion on barley as a result of direct transfer from timothy. However, the 

 writers were able to infect some plants in four of the five series of inoc- 

 ulations. The percentage of infections on barley is nearly as great as 

 that on oats and is greater than that on rye. The rust transferred very 

 readily to Dactylis glomeraia and fairly well to both Avena elatior {Arrhe- 

 natherum elaiius) and Avena fatua. It also transferred to Lolium perenne, 

 Lolium italicum, and Bromus tectorum. One extremely small pustule 

 developed on Elymus virginicus. 



The vigor of infection varied greatly on different hosts. In addition to 

 the inoculations indicated in Table I, many inoculations were made on 

 timothy. These nearly always resulted in a 100 per cent infection. 

 The incubation period on timothy was 7 to 8 days, while on barley it 

 was 10 to 12 days. It was clearly evident that barley was an unconge- 

 nial host; fairly large dead areas were frequently formed without subse- 

 quent development of pustules, and all pustules, when they did develop, 

 were extremely small. Most of the pustules were less than i mm. in 

 diameter, being mere dots in some cases. However, others were some- 

 what larger, some attaining a diameter of over i mm. On oats the pus- 

 tules were larger, the rust developing in a fairly normal manner. The 

 pustules on rye were fairly small, but there was not such a distinct tend- 

 ency to produce flecks as there was on barley. The infection on Avena 

 elatior, Avena fatua, Lolium perenne, and Lolium italicum was moderate, 

 while that on Dactylis glomerata w^as very severe, nearly as severe as that 

 on timothy. On Bromus tectorum the pustules were extremely small. 



Although the rust transferred fairly readily from timothy to both bar- 

 ley and oats, no infection was obtained on timothy as a result of inocu- 

 lations with Puccinia graminis hordei and Puccinia graminis avenae. 

 Less than 100 inoculations were made with Puccinia graminis hordei; in 

 no case, however, was there any indication of successful infection. The 

 transfer is entirely possible; more inoculations will therefore be made. 

 Timothy was inoculated directly with Puccinia graminis avenae, but 

 no infection resulted from any of 86 trials. No better results were 

 obtained by transferring first to Avena fatua, Phalaris canariensis, or 

 Dactylis glomerata. None of these forms, therefore, acted as a bridging 

 form between oats and timothy. It is possible that such bridging forms 

 may exist, although the possibility has not yet been demonstrated. 

 Carleton (i, p. 62) reported successful infection of Puccinia graminis 

 avenae on Phleum asperum. It is possible that this form might act as 

 a bridging species, but the writers have not yet had opportunity to 

 determine this. 



