Aug. is. 1914 
Head Smut of Sorghum and Maize 
35 7 
In an additional test intended to discover the influence of a residual 
effect of the fungicide after treatment without rinsing, it was found that 
the presence of a trace of copper sulphate in the medium does not hinder 
germination. However, Moore and Kellerman (1904, p. 29) found that 
the toxic, action of dilute watery solutions of copper is overcome by 
certain substances present in most culture media; and Hawkins (1913, 
p. 68-75) has recently shown that soluble calcium and potassium salts 
also neutralize the toxicity of copper. The probability that some of these 
substances were present in the vegetable medium used makes the above 
test of residual action inconclusive. Nevertheless, Dandeno (1908, p. 
60) states that UstUago zeae germinates readily in a N/2,048 watery solu¬ 
tion of copper sulphate. Copper fungicides do not appear to have a very 
penetrating action, and the sulphate certainly is not destructive to the 
head-smut spores within a limited time at ordinary temperatures. 
McAlpine (1910, p. 298) found that a 0.12 per cent solution of formal¬ 
dehyde did not affect the spores inside of 15 minutes. However, the 
formaldehyde treatment, when sufficiently severe, does kill them, as is 
shown in Nos. 1 to 10, inclusive, of Table III. These tests were with 
separate spores, except in the last three, in which spore balls were used. 
In spite of this evidence that the spores do not survive one hour's treat¬ 
ment with a 0.16 per cent formaldehyde solution, it was found that seed 
given this and more severe treatments produced plants with 4.2 per cent 
of infection in about 3,000 plants (the estimates in the early experiments 
were by heads) which survived, as against 3.4 per cent in about 2,000 
plants from untreated seed. The formalin treatment, therefore, is in¬ 
effective, but not because of failure to destroy external seed infection; 
and it may be said that this is true of the other chemical treatments of 
the seed, all of which have proved equally ineffective in prevention, even 
though, like copper sulphate, they may have had no lethal effect upon the 
spores. Indeed, plants from treated seed seemed the more easily infected 
in some instances. 
FLORAL INOCULATIONS 
The evident systemic character of the disease, however, immediately 
suggested the possible analogy with the loose smuts of barley and wheat. 
Kellerman’s inoculations were made before the possibility of intraseminal 
infection was realized, and the question occurs, was not Jensen's (1888, 
p. 61) mistake, in assuming extraseminal infection to have taken place in 
the case of Ustilago triiici when a diseased wheat plant appeared among 
those he had inoculated, here repeated in the case of sorghum ? While 
the loose character of the spore body and the echinulate spores of the 
head smut gave added force to the hypothesis of a floral infection, the 
abundant production of conidia and, as compared with the loose smuts 
(Appel and Riehm, 1911, p. 363), the prolonged viability of the spores, 
did not support this analogy. 
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