52 iBulletin No. 155
about five miles from the Experiment Station farm, on ,
which the wheat was never better than that year. When
soil is devoid of humus the soil grains run together,
forming a hard, compacted soil. When soil in this con-
dition is filled with water and freezes, the only release for
the consequent expansion is upward, and this of courses
causes "lifting" of the wheat. If the soil is well supplied
with humus, it has what is called crumb structure, which
gives it much greater pore space, consequently upon freezing
there is room for lateral movementof the soil upon expan-
sion and the wheat does not life, as in the other case. _
3. Treatment of Diseases.
There is never a year when one or' more of the diseases
_ which attack the wheat plant do not, in some sections,
materially reduce the yield of grain. Rust may in certain
seasons seriously affect the crop. Wheat scab shows up
occasionally, and while the loss from this disease is usually
light, it may reach as high as 10 per cent. ln 1909 scab was
very prevalent in Kentucky and most certainly reduced the
yield in many fields 10 per cent. In addition to these two
diseases, the smuts annually cause considerable loss in the
State. Other less destructive diseases attack the growing
wheat and exert their influence in reducing the yield, but
they are not nearly so important or destructive as the ones
mentioned. -
` These diseases are all due to the growth of parasitic
` fungi within the tissues of the wheat plant. These fungi
are slender colorless plants, although the masses of spores
may be colored, as the black smut spores and the reddish
rust spores. They appropriate the nourishment which
normally would go to increase the vigor of the wheat
'plant and make plump, perfect grains of wheat. They
reproduce by means of spores, which are very minute
objects, the individual spore being plainly discernible only
under a strong microscope. These spores correspond to
seeds in the higher plants. The life histories of some of