Feb. 16, 1924 
Flag Smut of Wheat 
459 
water, or distilled water, but that they germinate readily in a decoction 
of chestnut bark. The action of chestnut bark was not specific, for 
decoctions of material from trees belonging to other genera, and various 
nutrient agars, produced the same effect. 
Leach (26) found that spores of Colletotrichum lindemuthianum (Sacc. 
and Magnus) Briosi and Cavara germinated poorly in distilled water, but 
readily when small portions of the host tissue were present. 
Whitehead (55) reports that spores of Urocysiis cepulae Frost germinate 
slowly when sown in water, but much more rapidly and vigorously when 
they are sown in onion juice. 
In studies on the longevity of spores, Duggar (12) has shown that the 
spores of Aspergillus flavus Lk. and Sterigmatocystis nigra Britz would not 
germinate on the surface of distilled water, but when they were trans¬ 
ferred to a decoction of beans they germinated readily. Spores of this 
kind, however, are known to germinate readily on a wide range of 
nutrient media. 
Although plant tissues were so effective in stimulating the germination 
of spores of Urocystis tritici , the optimum effect could not be produced 
when the tissue was sown with the spores but only after the latter had 
gone through a “presoak” period. It is suggested that such procedure 
is necessary because of the nature of the spore wall and also because of 
the nature of the activating agent. The exact nature of the stimulatory 
substances in these instances is not known, but from subsequent tests it 
appears possible that a number of more or less simple substances may be 
operative. In the earlier tests several sections of wheat tissue were 
added to a few cubic centimeters of distilled water. Plant tissue de¬ 
coctions also were effective but these had to be in a suitable dilution. 
The concentration of the wheat tissue extracts will vary somewhat 
according to the conditions under which the seedlings are grown. In the 
following studies, seed of a number of common wheats was sown between 
sheets of moist blotting paper at 20° C. Six days later entire seedlings 
were ground in a meat chopper and the sap expressed with the aid of a 
hand press. It was found that a concentration of approximately 1 part 
per 10,000 was the most favorable for germination of the presoaked spores. 
At higher concentrations germination frequently was delayed. Pro my - 
celia sometimes were stunted and distorted and occasionally no spores 
germinated. 
The writer has recorded (55) that a steam distillate of a plant infusion 
also increased spore germination when satisfactory concentrations were 
used. 
Brown (6) has recorded the stimulative action of certain volatile 
products arising from the tissues of a number of plants on the germination 
of spores of Botrytis cinerea Pers., B. parasitica (allii ), Monilia fructigena 
Pers., Penicillium glaucum Lk., Fusarium sp. and Collecotrichum. He 
concludes that “while no exact rule can be laid down in this respect, one 
can say broadly that some plants give good stimulation, others less so. 
In some instances volatile materials appeared to inhibit the germination 
of the spores.” He also studied the effects of various chemical substances 
on the germination of spores of Botrytis and states that “a rough com¬ 
parison was made of several ethyl esters by testing the effect of a few cubic 
centimeters of a saturated watery solution of each and of a tenth dilution 
of the same on the germination of Botrytis in Petri dishes. In all cases 
inhibition was shown in the presence of the saturated solutions, while 
stimulation appeared over the tenth saturated solutions of ethyl acetate, 
malate, and citrate. Any further comparison was not attempted. . . .” 
