The progressive farmer. [volume] (Winston, N.C.) 1886-1904, 1886-06-30
was thought to be generally over
FROZEN SAP THEORY.

ing - AAOfe cCtt
ease to be caused by the freezing of
the sap in the winter. A poisonous
principle was thus induced, which
was carried to all parts of the tree
when the circulation became active
in the spring. 1t was called the
"Frozen Sap Theory" and was be-
lieved for a number of years to be
the explanation Of the disease.
FUNGUS THEoRY.
This was set forth as a cause of
the pear blight in 1868, and pub
lished in one of the Ohio agriculture
al reports. 1t found many support
ers. Some thought it due to cleo
trical disturbances, as it was often
more noticeable after a thunder
storm.
BACTERIAN THEORY.
We come now to the theory which
is supported by the best investiga-
tions and experiments of the present
day. Although bacteria had been
noticed in connection with the dis
ease prior to 1877, it was not sup
posed to be the cause. Prof. Burrill,
of Illinois, noticed bacteria in O
nection with it, and in 1878 stated
his belief that these organisms were
the cause of the disease. He per-
formed experiments in 1880 by inoc-
ulating healthy trees with the germs
from diseased ones and succeeded in
injecting those inoculated. In 1882
he named it m~icrococcus amylovo-
rus" which being interpreted means
the minute starch-eating berry. TO
be certain that these germs caused
the disease DR.. J. G. Arthur in 1885
separated the germs from the liquid
in which they were cultured. Trees
inoculated with the liquid show no
signs of the disease, while those in
oculated with the germs became in
fected. This demonstrated beyond
a doubt the truth of the bacterian
theory.
The m]icrococcus amylovOrus bur
is a one-celled organism generally
believed by scientists to be a plant,
but some eminent men believe the
bacteria to be animals. They lie on
the "border land" between plants
and animals. That is, they possess
the characters of both animals and
plants in so marked a degree that it
is difficult to say with certainty to
which kingdom they belong. Poll
ticians would say that they were
"straddle the fence"
HOW THEY ENTER THE TISSUES OF THE
1t has been found by numerous
experiments that the germs will not
enter through the bark except of
very tender twigs and when but lit
tie moisture is present; but the main
point of entrance is at the growing
bud or opening flowers. Wounds
produced by insects in the bark may
afford an entrance. The germs can
not penetrate through the skin of
the fruit, but when the fruit is af-
fected by an insect or when from
some other cause the skin becomes
punctured they can enter. 1t re-
quires some time, from two to three
or four weeks, after the germs enter
the tissues for the disease to become
apparent. The organisms consume
the oxygen in the starch of the
cells, thus breaking down the tissues
and causing death. When growing
these minute organisms hop about
with great alacrity, as can be seen
with the aid of a powerful micro
scope. By this movement and
through the circulation Of the sap
they r transported along the
branch. They are oval in shape. and
100000 to 100000 of an inch
long by 100000 to 3-1OO, 900 of an
inch broad. Arranged in single file
it would require about %, 900 to make
a line one inch long, or $4,000 placed
side by side to make a column of the
same length; or again, it would re-
quire 100000 of these little organ
isms to make a solid phalanx Of an
inch square!
The disease is of the nature of an
epidemic. 1t may appear in a local
ity SO as to do great harm with or
without a preceding year of slight
damage, and may be followed by one
or two years during which it may
be less virulent, followed by a longer
or shorter period of absence.
Earlier than 1916 it was some
times spoken Of as "frst cousin to
cholera" "a species of vegetable fer
ment," etc. In the year 1916 it was