27 
Hecke (14) and Kirchner (16) that bunt liability is not necessarily 
related to the varietal character of quick germination and rapid initial 
growth. Two series of tests of several varieties of wheat were made, 
in which the stage of development was observed daily. The notes on 
four of these varieties are given in Table 22. 
By reference to Tables 20 and 21 it will be seen that Turkey and 
Florence are the least bunt liable of all varieties tested and that 
Jones Winter Fife and Chul X Bluestem are extremely susceptible. 
The plant growth in Florence and Chul X Bluestem is equally rapid, 
while in Turkey and Jones Winter Fife the growth is equally slow. 
These tests were performed in the greenhouse. The grain was sown 
at a depth of exactly 2 inches, under conditions of soil temperature 
and moisture that were uniform during the period of observation. 
The grain used for seed was of the same age and was grown on the 
college farm at Pullman. 
It is not the wish here to controvert the view of Tubeuf (22, 23) 
and Appel and Gassner (3) that "the shorter the time between the 
initial germination and the appearance of the first leaf, the less the 
liability to infection, providing all other factors are equal." But the 
results of these experiments indicate that the differences in growth 
rate are varietal characters not necessarily related to bunt resistance. 
SUMMARY. 
Wind dissemination of spores was shown in 1915 to be the most 
important factor in the continued propagation of bunt in the Pacific 
Northwest, where the biennial crop system is practiced. 
Bunt spores lose their viability in 30 to 60 days in moist soil. 
Bunt spores in unbroken smut balls retain their viability throughout 
the winter months, even when subjected to alternate freezing and 
thawing, and they have produced infection after lying 1| years in 
the soil. 
When continually subject to the dry air of the laboratory or her- 
barium, bunt spores retain their germinating power for 12 years and 
possibly longer. 
The minimum, optimum, and maximum germination temperatures 
for Tilletia tritici are, respectively, to 1° C: 18° to 20° C; and 25° 
to 29.1° C. 
Wheat sown in soil at a temperature above 20° C. is practically 
immune from bunt infection from seed-borne spores, but not neces- 
sarily from spores already in the soil. 
Spores exposed five days to a temperature of 29.1° C. failed to 
germinate when changed to the optimum temperature. 
The presence of free oxygen is necessary to the germination and 
normal growth of the bunt organism. 
The optimum soil-moisture content for infection in the basaltic 
soil of the Palouse country lies between 16 and 30 per cent. 
The fungus may enter the wheat seedling at any point along tha 
coleoptile. 
Under experimental conditions infection may obtain after the 
seedling has produced its first leaf. 
There is direct correlation between the depth of sowing and the 
percentage of infection. 
Experimental study of a large number of varieties has demonstrated 
a wide range of susceptibility to bunt. The degree of varietal 
