462 
Journal of Agricultural Research voi. xxvti, no. 7 
In a number of tests benzaldehyde greatly stimulated germination. 
Its solubility is slight (0.3 part per 100 parts of water at 20° C.), but its 
boiling point is comparatively high (179.9 0 ). Thus, it appeared to be 
suitable for making comparative germination tests under laboratory 
conditions. A half-saturated solution of benzaldehyde in distilled water 
was prepared and this was used as a basis for subsequent dilutions. The 
results of one test are shown in Table III. 
At a concentration of 3 parts per 200,000, germination was delayed 
and subsequent growth of promycelia and germ tubes showed charac¬ 
teristic dwarfing and other abnormalities. This experiment was again 
repeated in duplicate and it was found that the most favorable concen¬ 
tration was again 3 parts per 2,000,000. It was found that spores sub¬ 
jected to concentrations of 3:20,000 for 18 hours at 20° C. revived when 
transferred to distilled water and germinated in a normal manner, but 
those exposed to concentrations of 3:2,ooo for the same period apparently 
had been killed. 
Germination at the optimum concentration was quite similar to that 
induced by the addition of small quantities of plant tissue as in previous 
experiments. In the latter instances, however, the germ tubes even¬ 
tually grew further than did those in the benzaldehyde solutions. 
Tabl,E III .—The effect of a solution of different concentrations of benzaldehyde in dis¬ 
tilled water on the germination of spores of Urocystis tritici presoaked at from i8° to 22° 
C.for six days prior to test , and transferred to solutions on January 8 
Num¬ 
ber of 
dish. 
Concentration. 
85 
86 
87 
88 
89 
90 
91 
92 
93 
94 
95 
96 
3 :20,000. 
3 :20,000. 
3 1200,000. 
3 :200,000. 
3 :2,000,000. 
3 :2,000,000. 
3 :20,000,000. 
3 12 0,000,000. 
3 :200,000,000,. 
3 :200,000,000. 
Control in distilled water 
.do. 
Percentage of germination on— 
j January 8. 
January 9. 
January 10. 
1 
0 
0 
0 
0 
0 
0 
i 0 
Trace. 
. 
0 
...do.... 
0 
86 
0 
80 
0 
Trace. 
0 
1 
0 
0 
0 
0 
0 
0 
0 
0 
1 0 
j 
0 
O 
A similar test with butyric acid resulted in germination of presoaked 
spores when sown in concentrations ranging from 1 part in 100,000 dis¬ 
tilled water (by volume) to 1 part per million. The optimum concentra¬ 
tion for germination of presoaked spores appeared to be 1 part per 500,000. 
The results of similar tests with other materials more or less soluble 
in water were not as striking as those given above. It is possible that 
they may have been less effective in any case, or that the effective range 
of concentration was more restricted. In some cases, however, it would 
appear that because of their great volatility the concentrations are more 
readily changed during the process of preparation of the dilutions and 
during the course of the experiment; hence their effect would not be so 
evident in experiments such as this. 
