By GRANT ALLEN.
If we were not so familiar with the fact, we would think there were
few queerer things in nature than the mode of growth followed by this
sprouting hyacinth bulb on my mantelpiece here. It is simply stuck in a
glass stand, filled with water, and there, with little aid from light or
sunshine, it goes through its whole development, like a piece of organic
clock-work as it is, running down slowly in its own appointed course.
For a bulb does not grow as an ordinary plant grows, solely by means of
carbon derived from the air under the influence of sunlight. What we call
its growth we ought rather to call its unfolding. It contains within
itself everything that is necessary for its own vital processes. Even if
I were to cover it up entirely, or put it in a warm, dark room, it would
sprout and unfold itself in exactly the same way as it does here in the
diffused light of my study. The leaves, it is true, would be blanched
and almost colorless, but the flowers would be just as brilliantly blue
as these which are now scenting the whole room with their delicious
fragrance. The question is, then, how can the hyacinth thus live and
grow without the apparent aid of sunlight, on which all vegetation is
ultimately based?
Of course, an ordinary plant, as everybody knows, derives all its energy
or motive-power from the sun. The green leaf is the organ upon which the
rays act. In its cells the waves of light propagated from the sun fall
upon the carbonic acid which the leaves drink in from the air, and by
their disintegrating power, liberate the oxygen while setting free the
carbon, to form the fuel and food-stuff of the plant. Side by side with
this operation the plant performs another, by building up the carbon thus
obtained into new combinations with the hydrogen obtained from its watery
sap. From these two elements the chief constituents of the vegetable
tissues are made up. Now the fact that they have been freed from the
oxygen with which they are generally combined gives them energy, as the
physicists call it, and, when they re-combine with oxygen, this energy
is again given out as heat, or motion. In burning a piece of wood or a
lump of coal, we are simply causing the oxygen to re-combine with these
energetic vegetable substances, and the result is that we get once more
the carbonic acid and water with which we started. But we all know that
such burning yields not only heat, but also visible motion. This motion
is clearly seen even in the draught of an ordinary chimney, and may be
much more distinctly recognized in such a machine as the steam-engine.
At first sight, all this seems to have very little connection with
hyacinth bulbs. Yet, if we look a little deeper into the question, we
shall see that a bulb and an engine have really a great many points
in common. Let us glance first at a somewhat simpler case, that of a
seed, such as a pea or a grain of wheat. Here we have a little sack of
starches and albumen laid up as nutriment for a sprouting plantlet.
These rich food-stuffs were elaborated in the leaves of the parent pea,
or in the tall haulms of the growing corn. They were carried by the sap
into the ripening fruit, and there, through one of those bits of vital
mechanism which we do not yet completely understand, they were selected
and laid by in the young seed. When the pea or the grain of wheat begins
to germinate, under the influence of warmth and moisture, a very slow
combustion really takes place. Oxygen from the air combines gradually
with the food-stuffs or fuels—call them which you will—contained in the
seed. Thus heat is evolved, which in some cases can be easily measured
with the thermometer, and felt by the naked hand—as, for example, in
the malting of barley. At the same time motion is produced; and this
motion, taking place in certain regular directions, results in what we
call the growth of a young plant. In different seeds this growth takes
different forms, but in all alike the central mechanical principle is the
same; certain cells are raised visibly above the surface of the earth,
and the motive-power which so raised them is the energy set free by
the combination of oxygen with their starches and albumens. Of course,
here, too, carbonic acid and water are the final products of the slow
combustion. The whole process is closely akin to the hatching of an
egg into a living chicken. But, as soon as the young plant has used up
all the material laid by for it by its mother, it is compelled to feed
itself just as much as the chicken when it emerges from the shell. The
plant does this by unfolding its leaves to the sunlight, and so begins to
assimilate fresh compounds of hydrogen and carbon on its own account.
Now it makes a great deal of difference to a sprouting seed whether
it is well or ill provided with such stored-up food-stuffs. Some very
small seeds have hardly any provision to go on upon; and the seedlings
of these, of course, must wither up and die if they do not catch the
sunlight as soon as they have first unfolded their tiny leaflets;
but other wiser plants have learnt by experience to lay by plenty of
starches, oils, or other useful materials in their seeds; and wherever
such a tendency has once faintly appeared, it has given such an advantage
to the species where it occurred, that it has been increased and
developed from generation to generation through natural selections. Now
what such plants do for their offspring, the hyacinth, and many others
like it, do for themselves. The lily family, at least in the temperate
regions, seldom grows into a tree-like form; but many of them have
acquired a habit which enables them to live on almost as well as trees
from season to season, though their leaves die down completely with each
recurring winter. If you cut open a hyacinth bulb, or, what is simpler
to experiment upon, an onion, you will find that it consists of several
short abortive leaves, or thick, fleshy scales. In these subterranean
leaves the plant stores up the food-stuffs elaborated by its green
portions during the summer; and there they lie the whole winter through,
ready to send up a flowering stem early in the succeeding spring. The
material in the old bulb is used up in thus producing leaves and blossoms
at the beginning of the second or third season; but fresh bulbs grow out
anew from its side, and in these the plant once more stores up fresh
material for the succeeding year’s growth.
The hyacinths which we keep in glasses on our mantelpieces represent such
a reserve of three or four years’ accumulation. They have purposely been
prevented from flowering, in order to make them produce finer trusses of
bloom when they are at length permitted to follow their own free will.
Thus the bulb contains material enough to send up leaves and blossoms
from its own resources; and it will do so even if grown entirely in the
dark. In that case the leaves will be pale yellow or faintly greenish,
because the true green pigment, which is the active agent of digestion,
can only be produced under the influence of light; whereas the flowers
will retain their proper color, because their pigment is always due to
oxidation alone, and is but little dependent upon the rays of sunshine.
Even if grown in an ordinary room, away from the window, the leaves
seldom assume their proper deep tone of full green; they are mainly
dependent on the food-stuffs laid by in the bulb, and do but little
active work on their own account. After the hyacinth has flowered, the
bulb is reduced to an empty and flaccid mass of watery brown scales.
Among all the lily kind, such devices for storing up useful material,
either in bulbs or in the very similar organs known as corms, are
extremely common. As a consequence, many of them produce unusually large
and showy flowers. Among our lilies we can boast of such beautiful
blossoms as the fritillary, the wild hyacinth, the meadow-saffron, and
the two pretty squills; while in our gardens the tiger lilies, tulips,
tuberoses, and many others belong to the same handsome bulbous group.
Closely allied families give us the bulb-bearing narcissus, daffodil,
snowdrop, amarylis, and Guernsey lily; the crocus, gladiolus, iris, and
corn-flag; while the neighboring tribe of orchids, most of which have
tubers, probably produce more ornamental flowers than any other family
of plants in the whole world. Among a widely different group we get
other herbs which lay by rich stores of starch, or similar nutritious
substances, in thickened underground branches, known as tubers; such,
for example, are the potato and the Jerusalem artichoke. Sometimes the
root itself is the storehouse for the accumulated food-stuffs, as in the
dahlia, the carrot, the radish, and the turnip. In all these cases, the
plant obviously derives benefit from the habit which it has acquired
of hiding away its reserve fund beneath the ground, where it is much
less likely to be discovered and eaten by its animal foes.—_“Knowledge”
Library._
* * * * *
History presents to us the life of nations, and finds nothing to write
about except wars and popular tumults: the years of peace appear only
as short pauses, interludes, a mark here and there. And just so is the
life of individuals a continued course of warfare, not at all in a
metaphorical way of speaking, with want or ennui, but in reality too
with his fellow men. He finds everywhere adversaries—lives in continual
struggles—and dies at last with arms in his hands. Yet, after all, as
our bodies must burst asunder if the weight of the atmosphere were to
be withdrawn from it, so, too, if the heavy burden of want, misery,
calamities, and the non-success of our exertions, were taken away from
the life of men, their arrogance would swell out, if not to the length
of explosion, at all events to the exhibition of the most unbridled
folly—nay, to madness. So that every man at all times requires a certain
_quantum_ of cares and sorrow, or necessities, as a ship does ballast, to
enable him to go forward steadily and in a direct line.—_Schopenhauer._