14 BULLETIN 1210, U. S. DEPARTMENT OF AGRICULTURE. 
by Schulthess (642), and Taylor (667) of England recommended i 
use at the rate of half a pound per bushel of seed. So far as the 
writers have been able to ascertain, Kuhn (22/1) was the first to inves- 
tigate carefully the effect of copper sulphate on bunt spores as well 
as upon the seed and to recommend a definite formula consisting of 
immersion for 12 to 14 hours in a 0.5 per cent solution. His further — 
experiments in 1873 (222) resulted in the conclusion that soaking ~ 
for 12 hours was suflicient and that injury to seed was negligible. 
He found that when compared with seed soaked 12 hours in water, — 
the treatment caused a slight reduction in the average number of 
roots but increased by about 30 per cent the sum total of root length. — 
He does not state the time interval between the beginning of the — 
germination experiment and measuring the roots, nor does he say — 
how the grain was threshed. 
Dreisch (101) conducted like investigations and came to a different — 
conclusion regarding seed injury caused by the copper sulphate. — 
Mle found that soaking in a solution as weak as 0.1 per cent for one~ 
hour resulted in root injury and inhibited germination by hardening the © 
testa of the grain. He further found that such seed showed a decided — 
difference in behavior when germinated in soil instead of in a moist 
chamber and that when sown in the ordinary way it suffered but 
little loss. He attributes this to lime in the soil and states that an 
aftertreatment with milk of lime counteracts the injury from copper 
sulphate. The only available abstract of Dreisch’s article says — 
nothing about the kind of seed used. It is entirely probable that 
the discrepancies between his results and those of Kthn are due to 
seed injury. 
Nobbe (287) had compared the effect of copper-sulphate treatment 
on hand-threshed and machine-threshed grain and found the latter 
to be much more susceptible to injury. He found, however, that 
grain with abraded seed coats germinated more promptly than sound 
seed, which fact he attributes to the more rapid absorption of water. 
Like Dreisch, he found that the soil neutralized the injurious effect 
of copper sulphate on the seed. He believed this was due to chemical 
reaction between soil substances and the copper sulphate in which 
the toxic property of the copper was destroyed. He found support 
for this belief in the results of an experiment in which 152.02 grams 
of air-dry soil was wet with 150 cubic centimeters of a 2 per cent 
solution of copper salt. This was filtered off and followed by 12 
washings. The total amount of filtrate was 2,240 cubic centimeters, 
and contained only 7 per cent of the copper salt originally added. 
Grassmann (/37) investigated the effect of copper sulphate on 
machine-threshed wheat, immersing the grain in solutions varying 
in strength from 0.1 to 2 per cent. He found that the 0.1 per cent 
solution caused but little injury, but that the injury increased with 
the strength of the solution, resulting in total loss of viability at 2 per 
cent strength. He found also that seed injury increased with the 
lapse of time between treatment and sowing for a period of 10 days. 
Seed treated with a 0.5 per cent solution 16 hours and tested for 
viability showed increasing injury as follows: 24 hours after treat- 
ment, 34 per cent; 48 hours, 43.07 per cent; 72 hours, 47.64 per cent; 
6 days after treatment, 51.33 per cent; 10 days after, 55.73 per cent. 
Jensen (184) announced the results of experiments involving the 
use of hot water for the prevention of smut. Up to this time his— 
studies were confined chiefly to oats and barley. This method, as 
