New-York tribune., 1900-08-12
STUDIES OF PLANT GROWTH.
EXHIBITIONS OF INSTINCT AKIN TO THAT
OF ANIMALS

OF ANIMALS.
From The Review of Reviews
The mechanism of plant adaptations is one
or the most interesting subjects in biology, and
some careful observations along this line are
published by Or. II. o. Juel, in the last num-
Der Of the "Jahrbucher Fur Wissenchaftliche
Botanik." Some writers compare the way in
winch plants sense external conditions and re-
spond to them with similar sensations and re-
sponses in animals. 1t is as difficult 10 make
close distinction between them as is is to make
distinction between plants and animals that
will hold in all cases. for the two great di-
visions of organic lie have much in common,
and If we are to accept the theories Of the
eVolutionists they are probably descended from
common ancestor possessing many of the
characteristics of both
A child may reach for a rod and take hold OF
1t, and a vine may swing its branches around
until 1t comes IN contact with the same rod,
and twine its tendrils around H. doing essentially
what the child has done; but as the child has
a nervous system and intelligence while the
plant has neither it is not easy TO explain the
relation between the two acts. These purpose
ful activities of the plant called trOpisms
There are number of them, and they of the
greatest Importance for the success of the plant
as an individual. By means of geOtroPlsm, the
plant grows root down and leaves up in the air
IN response to the force of gravity; but if it is
planted on a revolving wheel, where centrifugal
force will annihiIate gravity, it may be made to
grow, in defiance of plant tenets, with its root
in the air and its leaves down in the ground.
Certain plants have free moving forms, called
plasmodia- that will work their way along
against a current Of water; the network Of
the direction of current, and roots Of plants,
are also affected by the direction of current
Of water coming in contact with them
There are several tropisms to guide the seem
ingiy insensate root in it's blind wanderings
through the soil. GeOtropoism, heliotrop
ism. galvanotrOpiSIr. the responses to graV-
ity. light and electric currents, are local
lied in the root tip alone. and direct
its growth down into the earth and away
from light and electric currents when there
any Active growth of the root takes place just
above the tip; and in this zone are localized the
centres Of perception for hydrotrOpism, ther-
mOtropism, aerOtrOpism, by means Of which the
root is guided 70 moisture and away from heat
and the air.
JueI experimental on seedlings to find out
whether the laws governing their growth COM
PEELED them to turn against current or to grow
in the same direction. He planted the seeds on
pieces of cork placed wheel in such a way
that they projected into the water and allowed
it to flow freely around the roots they de-
veloped. The water was kept at a constant
temperature GO degrees c.. and the apparatus
was arranged that the rapidity of the cur
rent could be varied at will By fastening the
seeds in a definite position, the amount Of
growth in any direction could be accurately de-
termined, and as different parts of the root
vary in function, he also tried to find out in
which part the susceptibility to a current Of
water localized.
with slow moving currents responses were
uncertain, and defiIite results were obtained
but he succeeded with more rapid currents In
| one set of Indian corn seedlings, the tip was
cut off from part of the roots for about milli-
metre and a half. while the others were left
perfect. The uninjured roots turned against
| the current through angle of from 90 to 10
| degrees in twenty-fOur hours, and those with
| root tips cut off turned from D to 30 degrees
| in the same length of time Ten other sets, ex-
/ posed to a more rapid current turned through
| angles of from so to 40 degrees in twenty-five
| hours, with from 30 10 40 degrees for those with
| root tips cut off.
| On account of the turning Of the roots from
which the tips had been removed, Juel con-
| cludes that rheotrOpism or the power to turn
/ in response to the stimulus given by a current
| of water, must be located in the growing zone;
| and from the direction of the turning it is evil
| dent that there is something In the nature OF
! these roots that enables them to perceive the
| direction of the current and TO place themselves
! IN a definite position with regard to it,