198 BACTERIA IN RELATION TO PLANT DISEASES. 
Many experiments have been made with grains to free them from smut fungi and in 
this way considerable knowledge has been gained respecting the toleration of seed wheat, 
oats, etc., for hot water, copper salts and various other disinfectants. Some of the leading 
papers are mentioned under Literature. Only a few of the results will be cited here. 
Jensen who discovered the hot-water treatment for stinking smut (1888) advised 
temperatures between 127° and 133° F., and exposures of seed wheat and oats for not over 5 
minutes. He did not, however, determine accurately the thing we are here specially inter- 
ested in bringing out, namely, the killing temperature for the grains. 
In 1890, Arthur determined the effect of hot water on the germination of wheat. 
Wheat seeds immersed 5 minutes in water at 135° F. (57° C.) are not injured. Six hundred 
seeds exposed to 130° F. (54° C.) for 10 minutes also gave excellent results on germination— 
12.5 per cent in 24 hours and 93 per cent in 5 days. The injury to those treated 10 minutes 
at 135° F., and 5 minutes at 140° F. (60° C.) equaled about 20 per cent. The limit of germ- 
ination is 150° F. for 5 minutes (33 per cent). No germinations were obtained when wheat 
seeds were exposed to higher temperatures, e. g., 155° F. for 5 minutes, or to 150° F. for 10 
minutes. 
In 1891 Arthur tested the effect of hot water on oats, with especial reference to the 
prevention of loose smut. He states that the hot-water treatment—1o minutes in water 
at 135° F., or 5 minutes in water at 135° F. to 140° F. (57° C. to 60° C.) entirely destroys the 
smut while at the same time it improves the growth and increases the yield of oats. The 
water may be even as hot as 145° F. when the oatsare first put into it without much injuring 
the germination. Arthur made the exposures in cheese-cloth bags. 
Latta found 5 minutes’ exposure of oats in copper sulphate water (1 pound to 1 gallon) 
destroyed the smut but the germination was slower and the yield per acre was reduced. 
The comparative yields were: Hot water, 33 bushels; untreated, 28 bushels; coppered, 
24 bushels. Arthur, who reports this, tested the effect of copper sulphate on germination 
on lots of 200 seeds and obtained in the germinating chamber the following per cents: Hot 
water, 99; untreated, 98; copper sulphate, 67. Even in the soil where 98 per cent of the 
oats treated with copper sulphate finally germinated, they did so very slowly, the primary 
roots were often killed, and often they pushed out the plumule in advance of the roots. 
Kellerman & Swingle (1890) found that exposure of wheat at 139° to 140° F. for 15 
minutes destroyed nearly all of the kernels, 7.¢., on a plot that should have yielded 3,000 
or more heads there were only 9. Copper sulphate 8 per-cent, 24 hours, limed or unlimed, 
reduced the germinations about one-fourth. Copper sulphate 5 per cent 24 hours, unlimed, 
reduced the yield nearly one-third. Bordeaux mixture reduced the yield over one-fourth. 
Eau celeste, 24 hours (on another page the time is said to have been 36 hours) destroyed all. 
Carbolic acid 5 and ro per cent for 20 hours destroyed all. Mercuric chloride 1 per cent 
for 20 hours destroyed all. Potassium bichromate 5 per cent for 20 hours destroyed about 
half. 
According to Kellerman & Swingle (1891) oats which were treated at 141.8° F. (61° C.) 
for 5 minutes gave a good crop. The same result was obtained by exposing at 138.2° F. 
(59° C.) for 10 and for 15 minutes, 7.e., there was no destruction of the seed. Potassium 
sulphide 0.75 per cent and 0.5 per cent for 24 hours reduced the number of stalks about one- 
fourth. Copper sulphate 0.1 per cent for 24 hours reduced the number of heads about one- 
fourth. Copper sulphate 0.5 per cent for 24 hours reduced the number of heads nearly 
half. Copper nitrate in 5 per cent solution for 24 hours, limed or unlimed, destroyed most 
of the seeds. Even 2.5 per cent or 1 per cent greatly reduced the crop. Corrosive sublimate 
0.1 per cent for 24 hours réduced the yield three-fourths. Potassium bichromate 10 per 
cent for 23 hours killed all; same, 1 per cent for 9 hours, reduced the crop one-half or more. 
They recommend treating oats for smut by (1) hot water: temp. 132.5° F., time 15 
minutes; or, (2) potassium sulphide: 1 pound to 20 gallons of water, time 24 hours. 
