Feb. 16, 1924 
Flag Smut of Wheat 
463 
RELATION TO PRESOAKING 
Reference already has been made to a method of procedure which 
involved presoaking of the spores and subsequent addition of a stimu¬ 
latory agent, which resulted in an optimum germination of the spores 
of Urocystis tritici. 
Harrington (14) recently has reviewed the results of previous investi¬ 
gations on the presoaking of seeds of certain cereals and its relation to 
germination and subsequent growth of the plant. He also has studied 
the effect of presoaking “not after-ripened ,, seeds of cereals. Within 
certain limits the procedure had a beneficial effect. Many factor relation¬ 
ships apparently are concerned in the process, but the results indicated 
that changes in seed-coat permeability were chiefly involved. This author 
also mentions the work of Eberhardt, who has drawn the interest¬ 
ing conclusion that, although seed-coat permeabilities are increased, 
protoplasmic alterations also must be involved, as the effect was ob¬ 
served throughout the subsequent growing period. 
In a test to determine whether constant association with benzaldehyde 
in solution would result in germination of spores, results were obtained 
which were analogous to those previously reported by the writer (55) 
when plant tissues were used. 
In a few cases slight germination was noted after six days at 15 0 C., 
but in the majority of instances no spores germinated. These spores 
were viable, for they germinated on the readdition of the activating 
agent. It would appear that the activating agent had volatilized before 
it could penetrate and act upon the spore contents. This would explain 
why spores germinate more readily after presoaking than when sown 
directly on an activating solution. In the latter instance care has to 
be taken to prevent loss by volatilization, or allowances have to be made 
for it by using a more concentrated solution. In such a case there is 
danger that the more concentrated solutions may be more toxic to the 
spores. 
Thus, it seems most probable that the period of presoaking of spores 
in water results in an increased permeability of the spore envelope, as 
the spores respond with apparently equal vigor to the action of a stimulus 
within a presoak period of from 3 to 10 days at 20° C. This applies 
equally to spores sown on the surface of water and those totally immersed. 
There is undoubtedly some action on the spore contents also, but this 
appears to be only slight until after a sufficiently long period, when the 
spores germinate without the action of any special stimulus. 
ACTION OF STIMULUS 
The above results have indicated that many different substances 
stimulate the germination of the spores of Urocystis tritici . They differ 
widely in chemical composition, for they include acids, alcohols, ketones, 
aldehydes, and esters. There is no one individual substance which 
appeared to function as a specific activator of the protoplasm, such as 
was suggested by Thiel and Weiss (48) in their studies on teliospore 
germination. 
It is possible that these substances function partly by increasing the 
permeability of the spore envelope, although this appears improbable, 
as the presoak period is not materially shortened by their use. It would 
appear more probable that they function mainly in increasing the per¬ 
meability of the protoplasmic spore contents, and thus allow a more 
