A FOLIICOLOUS FORM OF SORGHUM SMUT AND NOTES ON INFECTION EXPERIMENTS.
On January 1st, 1900, several pots in the Botanical greenhouse of the Ohio State University were planted to sorghum, Kaffir corn, maize, sweet-corn and pop-corn. The seeds were previously moistened and mixed with a large quantity of head-smut of sorghum taken from smutted sorghum plants also from maize infected with the same fungus. This species was named _Ustilago reiliana_ by Kühn in 1868 from specimens collected in Egypt.
The plants developed rapidly and normally, though the stems were slender and did not reach the normal height. The panicles appeared early and only in a comparatively few cases showed infection.
In one case an anomalous specimen appeared, namely, a sweet corn plant with the upper leaves as well as the panicle infected. This form therefore differs from the type in being in part foliicolous and may be designated as _Ustilago_ (_Cintractia_[2]) _reiliana_ forma _foliicola_ nov. for. Figures 1 and 2, Plate 2, show the appearance of the infected plant, the one representing an earlier and the other a later stage of the emergence of the smut mass.
Mr. G. P. Clinton regards this fungus as a Cintractia rather than an Ustilago.
It may be remarked further that I have repeatedly tried seed inoculation experiments, mostly in the greenhouse but also occasionally in the field.
In the latter case in the summer of 1900, I obtained from a plot of many hundred stalks including field-corn, sweet-corn, pop-corn, sorghum, Kaffir corn and broom corn only three cases of smutted plants. These were of sweet-corn, both the tassel and ear being affected. The previous year about the same per cent. of successful inoculations were obtained. But in the greenhouse the experiments have uniformly resulted in the production of a considerable number of smutted stalks of sorghum and occasionally an infected plant of maize. These have for the most part been reported in print, the first account appearing in Bulletin No. 23, Kansas Experiment Station, in the year 1891.
I have now growing in the botanical greenhouse three sets of sorghum plants raised from seeds planted January 1, 1898, January 1, 1899, and January 1, 1900. Only the plants have been retained which showed successful inoculation experiments. They have been shifted to larger pots from time to time, but the plants make only a stunted growth. The new stalks that appear now and then are invariably affected, though sometimes one of the panicles, either the one terminating the main stem or one of the side branches may be free from visible smut. It is thus evident that this species of smut is perennial where its host lives from year to year. Figure 3 shows a photograph of one of the plants started in the greenhouse in 1899, its first stem producing an infected panicle. Figure 4 shows a plant grown in 1900, the first or central panicle not exhibiting the smut, but later when panicles from the side branches appeared, they were seen to be smutted.