Fort Worth weekly gazette. [volume] (Fort Worth, Tex.) 1882-1891, 1890-08-07

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 q new bark IL seen to De
forming underneath the old. The fact
that the disease in nearly every instance
has stopped progressing leads to the De-
lief that no more damage will bs 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 explaina-
ton of what microbs is would seem 10
be not out of place here. microOe, SO
called by modern scientists, is fungus
and fungus is, in botany, a peculiar
character of plant-growth represented III
the mushroom, the toadstool, mould on
decaying substances, mildew on taorlcs'
rust On wheat, smut on corn, ana so on.
Where fungus grows on living plant
il Is classed as a parasite, therefore tne
microbe causing pear blight is parasitic
growth.
A microbe is, so scientists tell us, the
smallest of all living and growing things.
Each individual microhe affecting the
pear tree is nearly spherical in shape, as
seen under the microscopes; in short, it is
IL
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 intinitesimal
size of individuals in this minute para
site may be gained when it Is stated that
/ il would take over 20, 900 of them 1,
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
| tremendous rate by division. MI
crobe absorbs little more juice from
| the pear tree, lengthens out slightly and
| forms construction in the middle. rms
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 a power of multiplication
which is only limited By the food supply
at hand. The microbe lives In the liquid
contents of the cells of the pear tree, ap-
propriating its substance and killing the
tissue as far as it peuetrates. The bark
of pear tree Is made up of minute cells
but each of these bark cells is near lOt
times larger than Que of the microbes
under consideration.
How these extremely small microbes
get through the walls of the bark cells
passing from Que to another, is not ye
| known to uaturalists.
Another question not yet settled Il
how these fungoid microbes manage II
get from one tree 10 another. The
theory Is that millions of them fall from
the infected trees and having been driet
out to extreme lightness are waited t
the next trees by the wind. Certain
is that they have some means OF travel
ing, for once a single tree is attacked tn
disease is apt to make run of the entir
pear orchard before it stops.
Such a thing as blight-proof pea
tree has not yet been discovered. Fo
years it vas claimed for the LIE Cont
pear that It was wholly bhght-proof
but this has turned out to be mistake
1t may be able to resist the trouble 20
greater degree than some OF the hne
varieties, but the blight gets it unde
favorable circumstances, as has bee
clearly demonstrated.