Feb. 16, 1924 
Flag Smut of Wheat 
455 
Stakman (43) records that neither Ktihn nor Brefeld was able to 
secure germination of fresh spores of Ustilago zeae (Beck.) Ung., but 
that Brefeld secured germination in nutrient media, although the 
spores did not germinate in water until the following spring. Stakman 
found also that, with the exception of one spore lot, a rest period was 
required before the spores would germinate. In a review of germina¬ 
tion studies on Tilletia levis Kuhnand T. tritici (Bjerk.) Wint., the 
same investigator reports the uncertain and capricious germination 
observed by Prevost, DeCandolle, Tulasne, Kuhn, Fischer von Waldheim, 
and Brefeld. Stakman (43) reports also that he was rarely able to 
secure germination of fresh spores, although he was successful in one 
instance (20 per cent being recorded) and then only when distilled water 
was used, but that after the spores had passed through a rest period of 
about eight months* duration almost 100 per cent of them germinated. 
It is recognized that distilled water is not always a satisfactory medium 
for the germination of spores, but this apparently is not always a limiting 
factor, for it is sometimes as effective as a “nutrient solution,” and some¬ 
times even more effective. 
MATERIAL AND METHODS 
The methods used were essentially the same as those previously re¬ 
ported (33). Germination studies were made in Syracuse dishes con¬ 
taining up to 5 cc. of medium. 
The spores used in practically all the tests were obtained from material 
collected in Illinois or from material produced in the greenhouses of the 
United States Department of Agriculture at Washington, D. C. This 
material was not more than 12 months old when used in the tests. Spores 
from material collected in Australia and Italy were used in a number 
of confirmatory tests made from time to time. 
MATURATION 
Reference already has been made to the fact that the age of the spore 
is sometimes a factor in determining its viability. A rest or maturation 
period apparently is necessary before the spores of many fungi can 
germinate. The teliospores of Puccinia graminis and the oospores of 
many Phycomycetes are familiar examples. 
Davis (jj), in germination studies on spores of Ustilago striaeformis 
(West.) Niess., states that the spores germinate when properly after- 
ripened. “The spores pass through an after-ripening period varying 
from 180 to 265 days.” The period of germinability is from 53 to 210 
days, and “nourishing solutions and decoctions are of no visible value 
in forcing the germination of these smut spores.** 
McAlpine (29) reports the result of germination studies with Urocystis 
fritici and has suggested that the age of the spore is a possible factor 
governing germination. He states: “Spores were taken from the 
wheat plant immediately after maturity and placed directly in water 
on a slide, but they did not germinate. With material, however, about a 
month old, and kept seven days on soil, a small proportion of the spores 
germinated in water after 24 hours.** He obtained up to 40 per cent 
of germinating spores in material several months old. 
74026—24-3 
