Iron County register., 1886-06-10
POTATO ROT.
The Tiny Parasitic Plant Which Causes
This Disease.

The Tiny Parasitic Plant Which Causes
This Disease.
Prof. j. H. Ponton, of the Ontario
Agricultural College, in an article on
this subject, writes: This disease has re-
ceived a great deal of attention from
botanists since the days when it became
a scourge in Ireland and other parts of
the British Isles. and it is now conceded
to be the result of minute fungus
called phytopthora infestans. This at
tacks all parts of the plant-leaf, stem
and tubes. By those ignorant of the
life history of this tiny parasitic plant
little attention is paid to its appearance
on the tops, and no alarm is expert
enced until the potatoes are affected.
But being very contagious, its presence
on the leaves should become a serious
matter, especially when we remember
that it spreads with great rapidity. 1t
is usually indicated by the tops pre-
senting a blotched, brownish, spot
ted, dead appearance. A close ex-
animation of the potatoes showing this
will discover innumerable slender stems
growing up out of the surface of the
leaves and stems of the affected plants.
These branch and swell out at the ends
into pear-shaped minute bodies (spores).
which are produced by millions. When
ripe they separate from the stem and,
being exceedingly light, pass into the
about. many of them finally reaching
the ground or settling upon plants. Un-
der favorable conditions of moisture
and heat the contents of microscopic
spore may push out a long, minute
tube. which can penetrate into any part
of the potato plant and give rise to the
fungus; or may separate into several
distinct portions (swarm spores), which
burst through the spore wall and be-
come the source of the parasitic plant.
The mature plant which lives in the
tops and tubers is very minute, and can
be seen only by the aid of the micro
scope. 1t consists of many colorless.
branching, thread-like structures. These
penetrate the tissues of the potato and
feed upon the juices, SO that it soon
weakens and begins to waste away.
From the thread-like structures tiny
stalks arise. assuming beautiful plant-like
forms and bearing upon their branches
the spores already referred to. They
live but short time, but the thread-like
structure is perennial and hardy, and
from fragments of it new fungi may
arise. 1t is said by some that another
kind of spore is produced which can
winter, and thus give rise to the organ
ism in another season These are the
so-called resting spores. apparently for
the purpose of keeping the species over
certain periods. while the spores already
considered are produced rapidly so as to
hasten the spread of the fungus under
favorable conditions. This minute
microscopic plant is certainly low
form of vegetable life, incapable of
manufacturing food from the mineral
kingdom, but fastening upon other
plants and feeding upon their juices. A
wet season supplies conditions well
adapted for its development, and hence
we find the ..rot'' associated with such
weather, There is no doubt that many
spores are always more or less present,
but they are prevented from being a
source of trouble because the weather is
not suited for their growth Chicago
Times.