61 
we can perhaps also judge of the behavior of the same germs in earth, 
and therefore in the soil of the field. It is scarcely to be supposed that 
the germs can be active in the deeper layers of the soil. It is much 
more probable that the condition for the vegetation of the smut fungi 
outside of the host plants is given only on the surface or in its vicinity, 
and that thence the host plants will be attacked by the smut germs.* 
But, now, before I pass to the infection experiments, i.e., to the pro¬ 
duction of smut diseases by infection with germs cultivated in nutrient 
substrata outside of the host plants, it may be judicious to state how 
extensive were the earlier experiments made directly and simply with 
the smut spores and to what results they have led. 
When the smut spores dispersed in water were brought upon the 
surface of that part of the host in which in smutted plants the smut 
appears the result was purely negative; neither the penetration of the 
fungous germ into the plant, nor the subsequent sickening of the same, 
was to be observed. According to this the places where the smut shows 
itself in the full-grown host plants and the places where its germs pene¬ 
trate into the plants could not well be the same. But neither on any 
other part of the full-grown plants was to be observed either the pen¬ 
etration of the germs or the subsequent appearance of the smut on the 
' infected spots. 
Following the earlier statements of Hoffmann it remained for J. Kilhn 
of Halle, an eminent authority in the domain of Mycology and especially 
in that of smuts and smut diseases, to select young seedlings as the 
subjects for further experiments and observations. Klihn was the first 
who showed in the case of the stone smut of wheat the germ threads of 
the Tilletia in the young seedlings near the root node. Then he suc¬ 
ceeded in doing the same thing in various forms of the genus Ustilago , 
after previous infection with the smut spores of these particular forms,— 
in Ustilago maydis , the corn smut, where three weeks after the infec¬ 
tion he found a smut pustule in the young axis of the seedling, during 
the development of which the plant died; in U. destruens, U. Grameri 
and 17. Tulasnei , on various kinds of millet seedlings ( Hirse Beimlingen ); 
and also in the dusty oat smut, U. carbo, and in U. bromivora on Bromus 
secalinus. In each case he was able to establish the existence of the 
mycelium of the smut fungus not only in the root node and its vicinity, 
but also in the first stem node and sheath-leaf node and in the in¬ 
ternode between these and the root node. Also at the same time, in 
these parts, he saw distinctly the points of penetration of the fungous 
germs. 
From his numerous experiments lasting many years, by which he 
* The experiments mentioned here upon the possible fermenting power of the smut 
yeasts, as well as the serial cultures themselves, were conducted with the most ex¬ 
traordinary care. The entrance of a single other yeast germ capable of causing fer¬ 
mentation would of course be enough to set up fermentation in the saccharine nutrient 
solutions and lead the experiments to wholly erroneous results. 
5461—Ko. 2-2 
