398 
The Pro}xigation and Prevention of Smut 
continuously grown for nearly thirty years ; and there also is 
a similar plot on which barley is grown every fourth year, in the 
following rotation, wheat, mangolds, barley, beans. In wheat 
smut never occurs, because the seed-corn is dressed with sulphate 
of copper. Now, if it were true that the spores which fell upon 
the ground were capable of producing the disease the follow- 
ing year in the crop, we should find the disease more prevalent 
in the first-mentioned plot than in the second, provided they 
were both sown with the same seed-barley. In 1885 and 1886 
the smutted ears were computed in the following manner : I 
walked slowly down the two plots for a distance of 120 yards, 
counting as I went along all the smutted ears which I could 
see on my left hand as I went, and on my right as I returned, 
with the following result : — 
Left Right 
In the plot sown every year with barley, 86 smutted ears ; 77 smutted ears. 
In the plot sown every 4th year „ 266 „ 302 „ 
Although by this means absolutely accurate results could not 
be obtained, yet it is conclusively shown that, contrary to what 
one would have expected, the plot which had been continuously 
cropped with barley was the most free from the disease. 
In 1886 a more exact method was adopted — namely, the per- 
centage of blighted ears was determined in the two plots with 
this result : — 
8,000 ears with plot continuously sown with barley, > 70 smutted ears. 
8,000 ears svith. plot sown every 4th year with barley . 130 „ 
The result was therefore the same ; there was much less smut in 
the plot continuously cropjied with barley, than in the one in 
which it was grown every fourth year. 
It has been often asserted that dressing seed-corn for smut 
is practically without benefit, because the crop becomes diseased 
from the spores which have fallen itpon the ground, unlike bunt 
(Tilletia tritici), in which disease the plants are infected from the 
spores adherent to the seed. The above observations, however, 
slaow this assertion to be incorrect. Further, the eminent 
Danish botanist Mr. P. Nielsen has tried to preserve the spores 
of smut by burying them at different depths in the ground. 
He experimented with myriads of spores, but found that, without 
exception, they all lost their power of germination between the 
end of summer and the following spring. 
Although the two plots above mentioned were sown with 
the same seed-corn, yet that which had been continuously 
cropped with barley had less smut in it than the other. This 
requires some explanation. When the young barley plants are 
attacked by U. secjctitm they become truly diseased, some to 
