Is there such similarity between animals and vegetables, in their
organic structure, development and functions, as to make it safe to
reason upon the properties of the one from the known properties of the
other?
It is admitted that the lowest forms of vegetable existence are
extremely difficult to be distinguished from a corresponding form of
animal existence. As we approach the lower confines of the vegetable
kingdom, flowers, and of course, seeds, disappear. The distinction
between leaves and stem ceases; and, at last, the stem and root are no
longer to be separated, and we find a mere vegetable sheet or lamina
whose upper surface is leaf and whose lower surface is root. In a
corresponding sphere, animal existence is reduced to its simplest
elements. Whatever resemblances there are in the lowest and
rudimentary forms of vegetable and animal life, it cannot be doubted
that when we rise to a more perfect organization, the two kingdom
become distinct and the structure and functions of each are in such a
sense peculiar to itself, that he will grossly misconceive the truth
who supposes a structure or a function to exist in a vegetable,
because such structure or function exists in an animal, and _vice
versâ_. To be sure, they resemble in _generals_ but they differ in
_specials_. Both begin in a seminal point but the seed is not
analogous; both develop—but not by an analogous growth; both require
food, but the selection, the digestion and the assimilation are
different. The mineral kingdom is the lowest. Out of it, by help of
the sun and air, the vegetable procures its materials of growth; in
turn the vegetable kingdom is the magazine from which the animal
kingdom is sustained; to each, thus the soil contains the original
elements; the vegetable is the chemical manipulator, and the animal,
the final recipient of its products. The habit of reasoning from one
to the other, of giving an idea of the one by illustrations drawn from
the other, especially in popular writings, will always be fruitful of
misconceptions and mistakes.
The next idea set forth in the paragraph which we review, is, the
_essential dissimilarity of buds and seeds_. The writer thinks that a
plant from a seed is a _new_ organization, but a plant from a bud or
graft (which is but a developed bud) is but a continuation of a
previous plant. With the exception of their integuments, a bud and a
seed are the _same thing_. A seed is a bud prepared for one set of
circumstances, and a bud is a seed prepared for another set of
circumstances—it is the same embryo in different garments. The seed
has been called, therefore, a “primary bud,” the difference beng one
of _condition_ and not of _nature_.
It is manifest, then, that the plant which springs from a bud is as
really a new plant as that which springs from a seed; and it is
equally true, that a seed may convey the weakness and diseases of its
parent with as much facility as a bud or a graft does. If the
feebleness of a tree is general, its functions languid, its secretions
thin, then a bud or graft will be feeble,—and so would be its seed; or
if a tree be thoroughly tainted with disease, the buds would not
escape, nor the tree springing from them—neither would its seed, or a
tree springing from it. A tree from a _bud_ of the Doyenne pear is
just as much a new tree as one from its _seed_.
The idea which we controvert has received encouragement from the fact,
that a bud produces a fruit like the parent tree, while, oftentimes, a
seed yields only a _variety_ of such fruit. But, it is probable that
this is never the case with seeds except when they have been brought
into a state of what Van Mons calls variation. In their natural and
uncultivated state, seeds will reproduce their parent with as much
fidelity as a bud or a graft.
The liability of a variety to run out, when propagated by bud or
graft, is not a whit greater than when propagated by seed, _in so far
as the nature of the vegetable is concerned_.
But it is true that the conditions in which a bud grows render it
liable to extrinsic ills not incidental to a plant springing from
seed. A seed, emitting its roots directly into the earth, is liable
only to its own ills; a bud or graft emitting roots, through the
alburnum of the stock on which it is established, into the earth, is
subject to the infirmities of the stock as well as to its own. Thus a
healthy seed produces a healthy plant. A healthy bud may produce a
feeble plant, because inoculated upon a diseased branch or stem.
Instead of a limitation in their nature, there is reason to suppose
that trees might flourish to an indefinite age were it not for
extrinsic difficulties. A tree, unlike an animal, is not a single,
simple organization, it is rather a _community_ of plants. Every bud
separately is an elementary plant, capable, if disjoined from the
branch, of becoming a tree by itself. In fact, each bud emits roots,
which, uniting together, go down upon a common support (the trunk) and
enter the earth, and are there put in connection with appropriate
food. Every fibre of root may be traced upward to its bud from which
it issued.
In process of time, the elongation of the trunk exposes it to
accidents; the branches are subject to the force of storms; in
proportion as the distance from the roots increases, and the longer
the passages through which the upper sap, or downward elaborated sap
travels, the more liabilities are there to stoppage and injury. The
reason of decline in a tree is not to be looked for in any exhaustion
of vital force in the organization itself, but it is to be found in
the immense surface and substance exposed to the wear and tear of the
elements.
It would seem, if this view be true, that no bounds can be placed to
the duration of perennial plants, if, by any means, we could diminish
their exposure, by reducing their expansion, by keeping them within a
certain sphere of growth. _Now this is exactly what is accomplished by
budding._ A bud, far removed on the parent stock from the root and
connected with it through a long trunk, is inoculated upon a new
stock. It now grows with a comparatively limited exposure to
interruption or accident. The connection with the soil is short and
direct.
In this manner a variety of fruit may be perpetuated to all
generations, _if the laws of vegetable health be regarded in the
process_. Healthy buds, worked upon healthy stocks and planted in
wholesome soil, will make healthy trees; and from these another
generation may proceed, and from these another. By a due regard to
vegetable physiology, the Newtown Pippin, and the Seckle Pear, may be
eaten two thousand years hence, _provided_, _always_, that expounders
of prophesy will allow us the use of the earth so long for orchard
purposes. A disregard of the laws of vegetable physiology in the
propagation of varieties, will, on the other hand, rapidly deteriorate
the most healthy sort. There is no clock-work in the branches of the
tree, which finally runs down past all winding up; there is no fixed
quantity of vitality, which a variety at length uses up, as a garrison
does its bread. Plants renew themselves and every year have a fresh
life, and, in this respect, they differ essentially from all forms of
animal existence. Any _one tree_ may wear out; but a _variety_, never.
We need not say, therefore, that we dissent from Knight’s theory of
natural exhaustion and from every supplement to it put forth since his
day. Van Mons’ theory of _variation_ and the tendency of plants to
return toward their original type, is to be regarded as nearer the
truth.