RUST-RESISTANT VARIETIES OF WHEAT 35 



1736, and Minnesota No. 163. There was no difference in the amount 

 of water until the plants germinated. Immediately after germination, 

 however, the soil in one series was kept very wet while that in another 

 series was kept as dry as was possible without endangering the life of 

 the plants. The soil in the wet series had a water content of 31.35 

 per cent, while that of the dry series was 6.16 per cent at the conclusion 

 of the experiment. Repeated trials were made with substantially the 

 same results. 



The number of einkorn and lumillo leaves which became infected 

 in the wet series was smaller than in the dry series. The percentages 

 for the others were practically the same. In virulence of infection, 

 however, there was considerable difference. The varieties also reacted 

 somewhat differently so each will be considered separately. 



On Kubanka the virulence of infection, especially in the early 

 stages, is very markedly inferior on the plants in the wet series. The 

 pustules during the early stages are often small and on some plants 

 do not appear at all, the leaf merely becoming yellow. Later the plants 

 in dry soil were often completely covered with large, vigorous pus- 

 tules while those in wet soil, although producing a moderately large 

 number of pustules, were not nearly so badly affected. In both series 

 there were many secondary infections along the leaf. There was a 

 distinct tendency in the wet series toward leaf-yellowing. It was at 

 first thought that the mycelium might be spreading through the tissues. 

 Histological examination, however, failed to confirm this supposition. 

 Apparently it was only a slight chlorotic condition due to excessive 

 water content. The infection was unquestionably more severe on plants 

 grown in dry soil (see Plate IV). 



On einkorn the differences were not so sharp, although there ap- 

 peared to be a slightly more severe infection on plants in the dry series 

 than on those in the wet series. The rust appeared at about the same 

 time, the virulence of infection being at first quite distinctly greater 

 on the dry-soil plants. Later this difference was not quite so marked, 

 although still apparent. 



The sharpest difference was on lumillo. Only a few leaves in the 

 wet series were really badly infected, while those of the dry series 

 showed a surprisingly virulent attack. There is no question but that 

 the infections secured on plants in these dry series were more severe 

 than were those on any other lumillo plants inoculated during the 

 various trials with this variety. It is not often that a "really vigorous 

 development of the fungus occurs on lumillo, but when the water con- 

 tent of the soil is very low, the infection at times shows surprising vir- 

 ulence (see Plate V). 



The results on Minnesota No. 163 varied more than those of the 

 other forms. The pustules in nearly every case were large and vigor- 



