Jan. 1905 ] Uredineous Infection Experiments 
27 
MAIZE RUST — PUCCINIA SORGHI Schweinitz. 
Inoculations with Puccinia sorghi were begun Jan. 16, 1904. 
Maize plants three to six inches grown in the greenhouse were 
used as hosts. The teleutospores were secured from infected 
Sweet Corn of the previous season, which had remained in the 
field all winter. The infections were tardy in bringing results, 
doubtless due in the main, to the unfavorable environment of the 
host plants; by this is meant that the quantity of light daily is 
much less than during the normal growing season in our latitude 
because of short days and much smoke and cloudiness in the 
atmosphere; and, besides, illumined as a greenhouse ordinarily is, 
a considerable quantity of solar light is excluded by the glass. 
In the first experiment, Jan. 16, 1904, (No. 261), Sweet Corn 
being used as the host, a well developed uredospore sorus was 
discovered on the under side of one of the leaves Feb. 10, but 
which must have appeared several days previous. 
A second inoculation with the teleutosporic material from 
the Sweet Corn as in the first inoculation, which was made Jan. 
22 (Expt. 262) produced several pustules of uredospores which 
were noticed and recorded Feb. 16. Some of the sori seemed to 
be perhaps three days old and others were barely rupturing the 
epidermis; they were a bright golden color, and it was a most- 
enchanting sight. As late as March 13 uredo-sori were found 
rupturing the epidermis of other host plants in the same pots and 
it is believed that they were also the result of the artificial inocu¬ 
lation with teleutospores and not from uredospores on the neigh¬ 
boring plants. 
Careful search was made continuously for the possible ap¬ 
pearance of spermogonia but here nor throughout the season could 
the slightest indication of such structures be detected. The 
appearance of uredospores following directly the sowing of 
teleutospores led to the conviction — corroborated by later experi¬ 
ments — that the spermogonia and secidia are not, at least in some 
cases, included in the cycle of development. The inoculation hav¬ 
ing been successful in mid-winter excluded even the slightest 
probability that accidental infection by aecidiospores or even 
uredospores had obtained. 
Uredospores obtained in the first experiment, where teleuto¬ 
spores from Sweet Corn in the field, sowed on Sweet Corn as the 
host, were used to inoculate Pop Corn (Expt. 280) March 30; 
at the same time other Sweet Corn plants were inoculated with 
like material. Uredospores appeared on both hosts April nth. 
Here as in most cases throughout the season teleutospores on the 
same leaves (different sori) appeared later. 
Common field corn, that is, Dent Corn, was inoculated April 
20 with uredospores from the Sweet Corn. Uredo sori appeared 
