The Milan exchange. (Milan, Gibson County, Tenn.) 1874-1978, 1880-05-06
Growth Of Plants.

Working Mems College, Great Ormond
Street, London, was given by Mr.. Fran
els Darwin, NJ. D., a son of the well
known naturalist. The growth of a
plant, the lecturer said might be likened
to the growth of SNOWFALL set rolling
down q snOw-cOvered hillside. Both
plant and SNOWFALL grew in size by the
addition of matter; but while, if the bulb
of hyacinth were placed in water and
kept in the dark, it would grow in the
ordinary sense of the word, in reality
the plant would merely have taken stuff
out of the bulb and arranged it in a diff
ferent way, whereas in the growth of an
oak tree from an acorn quantity of new
stuff was formed. These instances of
growth suggested the questions, first,
how a bulb or bean rearranged its mat
ter in forming q plant, and, secondly,
how all the new material was obtained
that went to form tree? He intended
on that occasion to speak of only one
half of the question: How the plant in
growing arranged its material? First,
it was necessary to know what 4 plant
was made of. If one hundred pounds
weight of some growing plant were
taken, say turnips, and the water driven
off by drying, it will be found that the
weight would have decreased by ninety
pounds, and that the solid, woody
part remaining, about ten pounds in
weight, would nearly all burn away,
leaving but a few ashes. In order to
give some idea of the way in which
this large quantity of water was
held in the plant, DR.. Darwin COM
pared the effect of water on dead matter,
such as tea leaves or leather, with the
effect of giving water to growing plant
the stiff, dry leaves became limp and
soft, while the dropping, faccid stem. of
a living plant, when watered, became
stiff and elastic. How could the plant
build up a strong, stiff stem with so much
of so unstable a material as water, and
how did the water become a source of
strength to the plant? To understand
this they must know how the water was
contained in the plant. The solid ma
terial was formed into little cavities, and
these-an infinite number of little boxes,
as it might be-were filed with water.
The way in which the water might be-
come a source of strength could be seen
by forcing water into a flexible tube or
bladder, or by blowing air into an empty
glove. The pressure of the water con-
tanned within caused the walls of the
cells to become stiff. There were other
ways, too, in which this stiffness was
obtained, the water getting into the text
ure of the woody stuff and stiffening it
as water stiffened sailcloth. This state of
things existed also in the pith, and each
cell, being Over-filled with water, was
forever trying to lengthen itself. Some
of the results of these conditions in
the plant were then explained by
the use Of two pieces of spiral spring,
and for a more familiar example
the audience were referred to the
effect of splitting a dandehOn stem.
Each half curled over outward because
the more elastic pith, trying to lengthen
itself, was prevented from expanding on
one side by the less elastic bark. With
two pieces of spiral spring in linen tube
it was pext explained how, when the
pressure of water in the cells in the two
halves of the pith was not equal, the stem
did not grow straight. Not that plants
bent accidentally or in purpOseless man
ner. On the contrary, when the plant
bent it was with some distinct and useful
object. To the explanation Of this point,
the rest of the lecture was directed The
direction and forms which the root and
stem of young growing plant might
take were happily illustrated with piece
of whitened lead pipe of small bore put
through cork, which did duty for the
bean. A great many theories had been
offered to account for the fact that the
root always tried to grow toward, and
the stem away from the center of earth.
Having related Andrew Knights ingen-
ious experiment with revolving wheel,
by which, with centrifugal force, as