62 
also unquestionably showed the smut disease in the full-grown plants 
after previous infection of the seedlings, Klihn reached the conclusion 
that the regular way for a successful infection with smut fungi was 
through the axis of the host plant in the first stage of germination. 
Besides Kuhn, R. Wolff also made successful infections with smut fungi 
in the botanical institute of De Bary in Halle. He repeated all the 
• 9 
earlier experiments as to the places of penetfation of the fungous germ 
into the host plants. In experiments which he made with Vstilago 
carbo , the dusty smut of oats, and Urocystis occulta , the stem smut of 
rye, he found that the germs of these fungi could not penetrate into the 
full-grown parts of the host plant; that only the sheath leaf of the 
young, just germinating host plants, is susceptiole and shows clearly 
places of penetration. In his experiments he sprayed his young plants 
with smut spores dispersed in water, making use of an atomizer to se¬ 
cure fine droplets, which alone would adhere to the surface. The 
plants were then kept moist under a bell glass in order to favor the 
germination of the smut spores on the surface and the penetration of 
the fungous threads. According to the conclusion which the author 
draws from the sum total of his experiments, the penetration of the 
fungous thread takes place in the young sheath-leaf of the seedling, 
and here only. The germs which have penetrated grow crosswise 
through the young leaves of the seedling till they reach their subse¬ 
quent nidus of development. This permeating growth was also ob¬ 
served directly in TJrocystis occulta. 
Moreover in this fungus, and only in this, was observed the appear¬ 
ance of the smut in full-grown rye plants which were infected in their 
youth. To these results reached by Wolff*, viz., that the sheath leaf of 
the young grain plant is the only place of penetration of the smut germ 
into the host plants, and that the germs grow crosswise through the 
young seedling and penetrate to the apex of growth—Klihn soon after 
replied with his complete array of proof, satisfactorily maintaining and 
additionally fortifying his earlier view. He points out that infection 
through the sheath leaf, which Wolff assumes to be exclusive, is uncer¬ 
tain, and that while in Urocystis occulta , according to his numerous and 
many-sided experiments, smutted rye can be i>roduced by infection of 
the sheath leaf, this is not possible in Ustilago carbo on barley, in U 
bromivora on Bromus secalinus , and in forms iu which the ovaries alone 
are smutted. He then sums up his experiences as follows: In all smut 
fungi which do not live in leaves, the result of infection through the 
sheath leaf is uncertain. Since these experiments by Klihn, which 
were made public in the Natural History Society in Halle in the begin¬ 
ning of 1874, no further accounts by other authors of infection experi¬ 
ments with grain smuts have appeared. 
For my experiments, to the communication of which I now proceed, 
I chose the dusty smut, Ustilago carbo , on oats and barley, the millet 
smut, U. cruenta on Sorghum saccharatum, and finally the corn smut, 
