Feb. 16,1924 Physiological Studies on Flag Smut of Wheat 431 
used. The soil and spore mixture constituting each sample was divided 
into duplicate portions, each of which was placed in a Syracuse watch 
glass and 3 cc. of tap water added to each. In one portion of each sample 
five wheat seeds were placed. After four days there was good spore 
germination in four of these portions in which seeds were germinating, 
but there was no germination in the duplicate portions without seeds, 
with the exception of one in which a single germinating spore was found. 
Also there were a few spores germinating in one other dish in which no 
seeds had been placed. After seven days there was good germination 
in four more cultures containing seeds, but there was no increase in germi¬ 
nation in the lots without seeds. 
Brown (j) recorded the stimulating effect of volatile substances 
arising from plant tissues on the germination of spores of Botrytis ci - 
nerea and other fungi. Plant distillates and various chemical substances 
also stimulated germination. Noble's data (jj) confirm Brown’s results 
on the effect of plant tissues and distillates on spore germination. He 
found that spores of Urocystis tritici “which had been presoaked in 
water for several days would germinate profusely after the addition of 
small quantities of wheat seedlings tissue.” 
VIABILITY OF SPORES 
In order to test the viability of spores of various ages, seeds of Harvest 
Queen (C. I. 5957) were inoculated with dry spores of Urocystis tritici , 
collected in different years and at various places, as given in Table II. 
The inoculations were made by mixing the seed with the spores in small 
seed envelopes. The inoculum used in this experiment was obtained 
from leaves which had been dried and kept at ordinary room tempera¬ 
ture under laboratory conditions. The inoculated seed was sown in the 
greenhouse and infection noted on the plants as they matured. The 
infection percentages are recorded in Table II. 
Table II .—The effect of age of spores of Urocystis tritici, and the locality in which they 
were produced, on the power to infect Harvest Queen wheat in the greenhouse at Arling¬ 
ton Experiment Farm, in IQ21-22 
Row 
number. 
Source of spores. 
Year. 
collected. 
j 
Wheat plants. 
Total 
number. 
i 
Number 
infected. 
Per cent 
infected. 
37 
Australia a . 
1919 1 
16 
16 
IOO 
55 
Granite City, Ill. 
1919 | 
14 
9 
64-3 
46 
Rosslyn, Va. 
1920 j 
17 
9 
5 2 -9 
64,73 
Do. 
1921 | 
3 i 
21 
67.7 
10,19,28 
Granite City, Ill. 
I 9 21 | 
! 
49 
23 
46.9 
a Spores obtained in 1921 from R. J. Noble. 
Table II shows that the spores produced in 1919 in Australia caused 
100 per cent infection, while the others were from 46.9 to 67.7 per cent 
effective. It may be that the fungus from Australia is more virulent 
than that obtained in the United States. However, these differences 
may not be significant, as was shown by the following experiment. Seed 
of Harvest Queen from the same source as that used in the previous ex- 
