BUNT, OR STINKING SMUT, OF WHEAT. 21 
further and more exhaustive study of the subject has been reported 
by Hurd (IS). Ocular evidence of the different responses of hand- 
threshed and machine-threshed wheat to treatment by copper sulphate 
and formaldehyde is presented in Plates I to V. 
The following facts are emphasized by these plates: 
(1) The desirability of instituting some method of threshing seed grain that 
will eliminate this loss, which certainly amounts to half of the seed sown where 
the copper-sulphate treatment is necessary. 
(2) In the case of machine-threshed grain the injury to germination by treat- 
ment with copper sulphate is almost as great from a five-minute bath as from 
one lasting an hour. 
(3) The injury by treatment with formaldehyde, while not nearly so great as 
that resulting from copper sulphate for a short period 'of exposure, increases 
continuously as the time of exposure is prolonged. 
(4) A comparison of the photographs of the pot cultures taken 28 and 40 
days after planting shows a higher power of recovery in plants grown from seed 
injured by copper sulphate than is the case with plants from seed injured by 
formaldehyde. 
If wheat must be sown in infested soil, the only control measures 
appear to be those indicated above, together with the introduction 
and adoption of the least bunt-liable varieties. There are, however, 
several possible means of avoiding the necessity of using such in- 
fested soil. 
The most important and practical of these are : 
(1) Collection and destruction of the spores at the threshing machine. 
(2) Sowing winter wheat before threshing begins; this is practicable in the 
less arid regions when harvest is comparatively late, if the summer fallow has 
been thoroughly cultivated and varieties of pronounced winter habit are used. 
Fortunately this method is applicable in that part of the country where the 
greatest bunt losses have occurred. 
(3) Replowing the summer fallow before seeding, so as to bury the spores 
below the seed bed. 
(4) Delaying seeding until sufficient time has elapsed after fall rains begin 
for the spores to germinate and die. 
(5) Spring seeding. 
(6) It may be possible to construct a drill attachment which would remove 
the infested soil from the immediate vicinity of the seed, where such soil is con- 
fined to the surface, as would be the case when no tillage has occurred after the 
smut shower. 
RELATION OF DEPTH OF SEEDING TO BUNT PRODUCTION. 
Whether or not the depth of seeding bears any relation to the 
production of bunt in the resulting crop seems not to have been 
investigated. 
Inasmuch as the plumule is susceptible to infection at any point 
below the surface of the soil, it would logically follow that where 
infective material was distributed throughout the seed bed, deep 
sowing would increase the liability to infection. However, there 
would remain the question as to what extent the harvest is affected by 
the location of the point of entrance of the fungus into the plumule. 
Experiments to determine the effect of the depth of seeding indicate 
that, in general, wheat plants possess the power to overcome infection, 
and that this power increases with the distance from the seed to the 
point of entrance of the fungus. This is shown by the proportion of 
partly bunted plants to those which are wholly bunted. (Table 17.) 
