Fort Worth daily gazette. (Fort Worth, Tex.) 1882-1891, 1890-08-03

disease has spread in larger patches on
the trunk, in the inner bark, but has
failed to kill the cambium layer next the
wood. Here new bark is seen to be
forming underneath the old. The fact
that the disease in nearly every instance
has stopped progressing leads to the be-
lief that no more damage will be done in
that particular year. The danger seems
to be over until the period for infection
next spring.
For the benefit of the readers not IA
miliar with scientific terms, an e1plaina-
ton of what q microbe is would seem to
be not out of place here. A mierobe, so
called by modern scientists, is fungus,
and fungus is, in botany, peculiar
character of plant-growth represented in
the mushroom, the toadstool, mould on
decaying substances, mildew on fabrics,
rust on wheat, smut on corn, aud so on.
Where fungus gr ows on a living plant
it IS classed as a parasite, therefore the
microbe causing pear blight is parasitic
growth.
A microbe is, so scientists tell us, the
smallest of all living and growing things.
Each individual microbe affecting the
pear tree is nearly spherical in shape, as
seen under the microscope; in short, it is
a simple and eolorless vegetable cell so
small as to be next door TO nothing. 1t
has no appendages of any sort, and no
spores to figure in its reproduction. as
many other species of fungi have. The
spread in the tree is brought about simply
by an increase of numbers due to division.
Some idea of the almost infinitesimaI
size of individuals in this minute para
site may be gained when it is stated that
. Nnl- Of hnn
placed IN line side by side, to measure
one inch. And yet these little cells, as
we may call them, kill large pear trees!
They make up in numbers what they
lack in size. These microbes multiply at
a tremendous rate by division. A mi
orobe absorbs a little more juice from
the pear tree, leugthens out slightly and
forms q construction in the middle. This
gradually deepens until the original cell
Is completely separated into two. These
fall apart, each one to again divide into
two, and so indefinitely. This process
gives them q power of multiplication
which is only limited by the food supply
at hand. The microbe lives in the liquid
conteuts of the cells of the pear tree, ap-
propriating its substance and killing the
tissue as far as it penetrates. The bark
of a pear tree is made up of minute cells,
but each of these bark cells is near 100
times larger than one of the microbes
under consideration.
How these extremely small microbes
get through the walls of the bark cells,
passing from one to another, is not yet
known to naturalsts.
Another question not yet settled is
how these fungoid microbes manage to
get from one tree to another. The
theory is that millions of them fall from
the infected trees and having been dried
out to extreme lightness are waited to
the next trees by the wind. Certain it
is that they have some means of travel
ing, for once a single tree is attacked the
disease is apt to make a run OF the entire
pear orchard before it stops.
Such thing as a bliRht-proof pear
tree has not yet been discovered. For
years it was claimed for the LIE Conte
pear that it was wholly blight proof,
but this has turned out TO be a mistake.
1t may be able to resist the trouble to
greater degree than some of the finer
varieties, but the blight gets it under
favorable circumstances, as has been
clearly demonstrated.