Infection of Host-Plants by Ustilaginecu. lo 



J 



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. segetiim 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. segetiim 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 more 

 U. segetiim 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 Tilletia 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 Ustilago segetuiii. See Descriptions. 



