RUST RESISTANCE IN WINTER-WHEAT VARIETIES. i) 
When sprays of urediniospore decoction were used in the study at 
Manhattan, Kas., a small knapsack pressure sprayer was employed. 
All sprays were applied in the evening; if possible during periods of 
moist, cloudy weather. The plants were first sprayed with water 
and then with the urediniospore spray. Sprays of urediniospores 
were found to be unreliable, however, because of the hot dry winds 
which frequently occur in Kansas during the late spring and early 
summer. In order partially to overcome this difficulty, removable 
canvas covers were placed over a wooden framework which was 
built over the plats. These covers were used the day following the 
urediniospore sprays and aided materially in retaining moisture. 
They were easily handled by one man, being unrolled from a long 
strip of wood and drawn over the nursery plats, to be fastened at 
the corners as shown in Plate II, figure 1. 
Several attempts have been snags to inoculate plats | in the rust 
nursery in the fall. Not only was it difficult to obtain satisfactory 
infection, but it was of doubtful value in view of the fact that it is 
Hoe aah whether stem rust lives over winter in Kansas to oa: 
great extent (17). 
On account of the unsatisfactory results obtained with the uredin- 
iospore sprays, the infection-center method of obtaiing an epidemic 
was tried. This method is somewhat similar to inoculating plants 
in the field, but 1t is much simpler and more certain to give satis- 
factory results. The inoculated seedlings are carried from the green- 
house to the plats, where they spread the infection. Numerous 
infection centers were located in each plat, so as to provide ample 
spore material (Pl. II, fig. 2). 
Most of the rust cultures for these experiments were grown on 
seedlings in 24-inch flowerpots, two seedlings in each pot. Fre- 
snes nck pots were used, as they held more seedlings and did 
not dry out so rapidly. It was found that if small galvanized-iron 
pans were placed between the rows of wheat in the rust nursery 
early in the spring and filled with pots of inoculated seedlings, a 
most successful center of infection could be established. (Pl. II,- 
fig. 2). The pans were kept filled with water at all times. 
. As soon as the seedlings died or the rusted leaves-no longer produced 
urediniospores, the pots were replaced with a new set. In this man- 
ner the wheat plats were continually exposed to rust infection. _ It 
recently has been found that if plants in the heading stage are inocu- 
lated in the greenhouse and used in place of seedlings for the centers 
of infection, their usefulness in the field continues longer than that 
of seedling plants; hence, they are much more satisfactory. It was 
found also that wherever the centers of infection were located the 
rust obtained a start and spread rapidly from the centers to all 
- adjacent plants. 
