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the same to prepare the land, plant and harvest the grain crop 
when the yield is half smut as it does when it is all clean sound 
grain. The question of the prevention of plant diseases is thus 
one of very great practical importance. Vegetable pathology is 
one of the newest of the biological sciences. What we know of 
it has practically all been learned during the past thirty years. 
I remember that when in college during the seventies the only 
known remedies for plant diseases were that sulphur sprinkled on 
rose bushes and grape vines would, to some extent, prevent 
mildew, and that soaking seed oats in a weak solution of copper 
sulphate would prevent smut in the following crop. At least there 
was a popular impression that these were facts, but no conclusive 
experiments in regard to them had been recorded. Now the list 
of preventable or partially preventable diseases is a very long 
one. The number of remedial measures used is also considerable. 
With the environmental diseases the obvious remedy is to 
correct the unfavorable conditions. If the ground is too wet, 
drain it. If too dry irrigate it, or cultivate so as to conserve 
moisture. If poor in plant food, fertilize it. Or if a certain crop 
is not suited to the prevailing conditions grow some other crop 
that will find them congenial. These I say are obvious methods 
for preventing troubles of this kind and yet the problem is by no 
means a simple one. In only too many cases we are unable to 
predict without actual trial whether or not a given crop will 
thrive under new and untried surroundings. 
Our knowledge of the functional diseases is not yet sufficient 
to permit the suggestion of remedies. They must still, for the 
most part, be classed as incurable. We may know, as in the 
case of the aster “ yellow eee. that an insufficient secretion 
s 
and consequently is unpreventable. No group of diseases is 
more urgently in need of farther investigation than these. 
It is in the controlling and preventing of parasitic diseases that 
modern progress has been most marked. Remedial measures 
that may be employed against them can best be considered under 
the headings hygiene, topical applications and heredity. 
