BUST RESISTAlsTCE . IN WINTER- WHEAT VARIETIES, 17 



size to accommodate about 72 plants. About half an inch of water 

 was kept in the bottom of the chamber and a pan of water was sus- 

 pended from the top. A cloth wick was placed over this pan and 

 was allowed to hang down on two sides, as shown in Plate IX. 

 This helped to keep the air saturated. A glass top allowed sufficient 

 light to enter the moist chamber, so that the plants did not become 

 etiolated during the incubation period. On warm days a stream of 

 water was allowed to flow over the top, as illustrated in Plate X. 

 This helped to maintain a . cool temperature within the chamber. 

 Cloths were hung over the outside walls to help distribute the water 

 evenly. An overflow pipe in the pan at the bottom of the chamber 

 carried away the surplus water. The inoculated plants were placed 

 on inverted empty flowerpots, to avoid setting them in water. 



RESULTS OF THE GREENHOUSE EXPERIMENTS. 



The results obtained from greenhouse inoculations are shown in 

 Table 3. Very heavy infection always was obtained on the checks 

 and the susceptible varieties, but in the case of Kanred, P1066, and 

 Pi 068 no uredinia appeared. Some of the spring- wheat varieties 

 also showed only slight to moderate infection. The peduncles, 

 glumes, and awns of all susceptible varieties were just as readily 

 infected at heading time as were the seedlings. In the case of the 

 three resistant varieties, if any portion of the head becomes infected 

 it is the awn. No signs of infection, however, could be noticed on 

 plants of the three resistant varieties with the exception of a few 

 indefinite flecks on the culms. A plant of Improved Turkey was 

 included with each set of varieties and on being inoculated was 

 placed in the damp chamber and maintained luider the same condi- 

 tions. These checks always became heavily infected. It is evident 

 that favorable conditions for infection were present, as uredinia were 

 produced on plants of Khapli emmer (C. I. No. 4013), Kubanka 

 durum (C. I. No. 2094), and other varieties of emmer and durum 

 wheat which are known to be resistant to stem rust. 



The " type of infection," is shown in the table by symbols (explained 

 below) indicating the relative resistance or susceptibility. The 

 results of inoculations in the seedling and heading stages should be 

 regarded as a corollary to the field results, however. It is hardly 

 safe to draw final conclusions on the comparative resistance of va- 

 rieties from experiments in the seedling stage alone, as the conditions 

 under which the inoculations must be made are certain to vary and 

 frequently may cause a different interpretation of the results. This 

 is especially true where only a few seedlings are inoculated. A variety 

 inoculated with a given strain of stem rust may show a somewhat 

 different type of infection when inoculated at another time, even 

 though the check which is run with every series may show a normal 

 infection. 



