Infection of Host-Plants by Ustilaginee. 103 
ro) 
while they were in flower, but the plants were subsequently 
destroyed by an accident. 
Recently Mr. J. L. Jensen has published the results 
of his experiments and observations conducted on the ex- 
perimental farm of the Royal Agricultural School near 
Copenhagen. He believes the spores of U. segetum effect 
their entrance into the host-plant at the time it is flowering, 
and either infect the ovum or remain quiescent, enclosed 
within the grain until the ensuing spring, when they 
germinate when the grain does, and so cause its infection. 
He found that barley grown for twenty-five years con- 
secutively upon one experimental plot was not more affected 
with U. segetum than when grown in the ordinary rotation 
with other crops, which clearly shows the teleutospores do 
not remain effective in the soil. He further found that 
manuring with ‘farmyard manure does not produce moré 
U. segetum in the crop than occurred when artificial 
manures were employed. But he did find that seed 
obtained from a field in which the fungus had been 
abundant produced a more severely diseased crop than 
when the seed was taken from a healthy field ; but that, if 
the seed oats were dipped in water at a temperature of 57°C. 
(134° F.), and allowed to remain there for five minutes, the 
disease was prevented, and, moreover, the vitality of the 
seed was unimpaired.* 
With regard to 7iletia tritici, the important question 
of the protective dressing of the seed corn has long ago 
engaged the attention of agriculturists. Many have been 
employed, but that most generally used (and probably the 
best) is a ‘5 % solution of cupric sulphate in water. Alum, 
ferrous sulphate, and even sulphuric acid, unless used 
sufficiently concentrated to injure the seed corn, were 
* Some additional observations of Mr. Jensen on this subject, made during 
the year 1888, will be found under Usti/ago segetum, See Descriptions. 
