412 The Propagation and Prevention of Smut 
The question presents itself, why do sulphuric acid, sulphate \ 
of copper, and warm water, as previously described, kill the 
smut in oats and not in barley, although all the spores adhering ' 
externally were proved to be killed ? I think it is because the | 
barley is closely and completely invested by its husk, while the 
oats are not ; so that the disinfecting solution can freely ent«r 
the space between the husk and the kernel and act on the spores 
in the latter, and not in the former. With barley the disin- 
fecting solution cannot amve at the kernel without soaking 
through its outer coating, and in so doing, as chemists tell us, a i 
solution of sulphate of copper would by osmosis be materially ' 
reduced in strength by the time it reached the kernel. Thus it is | 
that the germinative power of barley is apparently not injured I 
by comparatively strong copper solutions. In like manner the ' 
reason that dipping barley for five minutes in warm water is 
without effect on the smut is because the water had not time to 
soak through and get to the kernel, and, therefore, the included I 
spores were only subjected to a dry heat, which, as we have 
seen, is comparatively easily withstood by the spores. If we 
suppose the barley kernel to be pervaded by a mycelivmi the 
same explanation obtains. It seemed probable that by first 
soaking the barley for a longer period, such as half a day or a 
day, and then dipping it into heated water, complete disinfection 
could be obtained. This has been confirmed in the most satis- 
factory manner by Mr. C. F. Jensen of Rodstenseje, who this year 
(1888) at my suggestion treated all his seed-barley (about 200 
bushels) by steeping it in cold water for half a day and then j 
dipping it for five minutes in water heated to 127° F., with the ; 
following result : — 
2,000 unprotected barley plants had 45 smutted. 
2,000 treated with warm water as above, none smutted. 
In fact, in the whole field of protected barley only a single 
smutted plant was found. The germinative power of the 
barley was unimpaired ; it is now (August 6) growing luxuriantly 
and promises to produce a heavy crop. It must be observed j 
that steeped barley will not stand more than 127° F. without 
injury, but when only sprinkled with water 133°F. for five | 
minutes will not injure it. This last proceeding, however, does 
not appear to be so eflicacious. 
Is it necessary to repeat the protective dressing for smut every 
year ? Probably not, because smut propagates itself comparatively j 
slowly. The rate of increase in the dift'erent varieties of oats > 
grown on the experimental farm at Copenhagen cannot be taken 
as a guide on this point, because these varieties were grown in 
i 
