596 
Journal of Agricultural Research 
Vol. XXIV, Na f 
determined by the number produced on first observation, the optimum 
temperature for sporidial production lies between 26.5° and 34.7° C. 
The maximum lies between 36° and 38°. Of 20 observations above 34° 
only 4 showed abundant production. 
At the low temperatures, wherever germination took place sporidia 
also were produced. The number of cells in the basidia and the width of 
basidia were alike at the different temperatures and so could not be 
used as criteria in establishing the optimum temperatures. The lengths 
of basidia and condition of cellular contents, as shown in Table I, differed 
at 36.1° to 37.8^^ C. from those at other temperatures, indicating a 
deviation from normal at this high temperature. As below 26.5° the 
percentage of germination is decreased, and, as above 34.7° the sporidial 
production is decreased and germ tubes are abnormal, the optimum tem¬ 
perature for spore germination may be stated as between about 26® and 
34° C. As Table I shows that the maximum temperature rests between 
37.1° and 37.8° and as six experiments show no germination at tempera¬ 
tures above 38° after two weeks, the maximum temperature for germi¬ 
nation apparently lies between 37® and 38° C. 
Attention should be called to the fact that this optimum temperature 
for germination is much higher for Ustilago zeae than for other smuts 
which have been studied in this laboratory. For example, Ustilago 
avenae germinates best between 15*^ and 28° C., and, according to Volkart 
(9), Tilletia tritici (Bjerk.) Wint. and T. laevis Kuhn germinate best 
between 16° and 18® C. 
SUMMARY AND CONCLUSIONS 
(1) In 27 trials to germinate Ustilago zeae spores in soils containing dif¬ 
ferent amounts of manure, there was considerable germination in only 
one, slight germination in another, and germination barely occurring in 
a third. The spores germinated readily in many artificial media, from 
among which Pasteur’s solution was chosen for the experiments to 
determine the relation of temperature to spore germination. 
(2) The optimum temperature for the germination of Ustilago zeae 
spores was found to lie between about 26® and 34° C., the maximum be¬ 
tween 36® and 38®, and germination was observed to occur at the mini¬ 
mum temperature of 8®. The optimum for sporidial production lies also 
between about 26° and 34° C., the maximum between 36° and 38°, and 
sporidia are produced at the lowest temperatures at which germination 
was observed. 
(3) The experiments showing that high temperature is most favorable 
for spore germination indicate that infection likewise is favored by hot 
weather whether the germination takes place in the soil or in water held 
upon the host plant. 
LITKRATURB CITED 
(1) Arthur, J. C., and Stuart, Wm. 
1900. CORN SMUT. In 12th Ann. Rpt. Ind. Agr. Exp. Sta. [18981/99, p. 84-135, 
I fig., pi. 10-13. Bibliography, p. 130-135. 
(2) Brefeld, Oscar. 
1883. UNTERSUCHUNGEN AUS DEM GESAMMTGEBIET DER MYKOEOGIE. V. Heft: 
Die Brandpilze I ... vi, 220 p., 13 pi. Leipzig. 
(3) Clinton, G. P. 
1900. THE SMUTS OF ILLINOIS’agricultural PLANTS. In Ill. Agr. Exp. Sta. 
Bui. 57, p. 289-360, illus. 
