in Oats and Barley. 
401 
In a field of smutted oat or barley the spores of the smut 
fungus (U. segetum) are swarming in great quantities, and 
may be found by microscopic examination on all parts of the 
healthy plants, even upon the kernels themselves. It is also a 
well-known fact that using seed from a smutted field, unless it 
be efficiently dressed, will produce a smutted crop ; and, more- 
over, the more smutted plants there are in the field of seed- 
corn, the greater will be the number of diseased plants produced 
from its seed. 
Up to the present it has always been considered that the 
cause of this was the spores which adhered to the seed-corn. I 
have, however, for some years made a considerable number of 
experiments by sowing the live spores of smut upon oat and 
barley-seed taken from healthy fields without being able to 
produce smutted plants, while the crops always became smutted 
when produced from seed taken from a smutted field. I, there- 
fore, began to doubt whether the adherent spores on the seed- 
corn could have had anything to do with the production of the 
disease. 
This doubt was strengthened by a communication from Mr. 
Plowriglit, in which he told me that in ten experiments with 
oats he had tried in vain to produce a smutted crop by sowing 
the seed-corn with the spores of {U. segetum) partly with the 
ordinary spores, partly with the secondary spores before men- 
tioned. In the summer of 1887, I made the following experi- 
ments, which bring out this point very clearly : — 
Aquantity of oats was taken from a field in wLicli more than 40 per cent, 
of the ears were smutted. It was divided into three portions, A., B., and 0. 
A. was washed with water and fine sand ; each grain was found on ex- 
amination to have on an average 60 spores adhering to it. and then planted. 
B. was planted without any preparation ; about 8,000 spores adhered to 
each grain. C. was dusted with spores, so that about 40,000 adhered to each 
grain, and then planted. 
The germinative power of the spores was tested, and it was found that 
each grain in A. had 25 living spores on it, in B. 4,000, and in 0. l:i,000. 
A quantity of barley taken from a smutted field was treated in the same 
way. 
The above were sown, with the following results :— 
Oats. 
A. 25 living spores on each grain produced 29 per cent, smutted eara. 
B. 4,000 „ „ „ 37 
C. 12,000 „ „ „ 38 
A. washed, and having very few living spores on 
each grain . . . . . . 1'6 per cent, smutted ears, 
B. unwashed, with many living spores on each 
grain ]-4 „ „ 
C. dusted with additional sspores on each grain 1-4 „ „ 
VOL. XXIV. — S. 8. D D 
