71 
one case 1 per cent., in the other 2 per cent, of smutty plants; in two 
additional series no smutty plants ; barley sound. 
IX. Experiments with larger plants by external infection and by 
infection in the heart of the growing tip, were wholly without result. 
The final result of the experiments with oats may be summed up as 
follows: The infection most productive of results is upon the barely 
germinating young seedlings, just as it was previously stated by Kuhn. 
The exclusive infection of the sheath leaf is fruitful, as a rule, only 
in the youngest stages of the same. The infection is without result as 
soon as the inner leaves have pushed through the sheath leaf more 
than 1cm.; from this point on the plants are proof against the fungous 
germ. By the use of nutrient substrata for the conidia sproutings, 
consequently by means of earth treated to fresh horse dung, the infec¬ 
tion of the young seedlings will be greatly increased and the spread of 
the smut very materially promoted,* corresponding to the experience of 
husbandmen in the use of fresh dung in the field. Smut germs, which 
have lived too long and too exclusively outside of the host plant and 
multiplied in the form of sprout conidia, lose their infective power con¬ 
jointly with the ability to throw out germ tubes. 
But how are the negative results of the experiments to be inter¬ 
preted ? First , how is it to be explained that even in the most favor¬ 
able cases only a large per cent, of the experimental plants become 
smutty and not all which were infected ? And, second, whence comes 
it that in all exj)eriments with barley in not one single case did a 
plant become smutty ? 
* The influence of fresh dung on the production of grain smuts diminishes quickly 
with the age of the dung, because the conidia germinated in it perish, and in old 
rotten dung the smut spores develop imperfectly or not at all. The less wet the dung 
the more slowly decay takes place, and the longer the smut germs can maintain them¬ 
selves in it. 
In the dung of horses, and of swine also, are to be found many oat and barley 
grains which have not been digested and which subsequently germinate in the dung. 
Many times by the hundred in root fields I have come across such germinated barley 
grains, accidentally transported into the field with the fresh swine dung, and have 
found that for the most part they bring forth smutty spikes. This bears most strik¬ 
ing v itness to the effect of fresh dung in the spreading of smut and in the appear¬ 
ance of smut in freshly manured fields. In isolated cases, in small fields, I have 
gathered the smutted spikes in thick bundles, and have found that out of 100 barley 
plants were to be found only 10 to 15 sound spikes. It need not bo said that in 
these cases I have each time inquired very exactly and particularly concerning the 
way of manuring. 
