The kernel is usually composed of the albumen, cotyledon, and embryo.

The Albumen is that part of the kernel which invests the cotyledons or lobes, and is thought to afford the same support to the germinating embryo, that the white of an egg does to a chicken. Both in respect to hardness and colour, the albumen, in many seeds, greatly resembles the white of a boiled egg. It is not considered an essential part of the seed, because it is sometimes wanting; but when present, it supports and defends the embryo while imprisoned in the seed, and serves for nutriment when it begins to germinate. It has no connexion with the embryo, and is always so distinct as to be easily detached from it. Albumen makes up the chief part of some seeds, as the grasses, corn, &c.; in the nutmeg, which has very small cotyledons, it is remarkable for its variegated appearance and aromatic quality. It chiefly abounds in plants which are furnished with but one cotyledon.

d

Fig. 110.

Fig. 110 represents the cotyledons of the bean, as divested of the husk; a, represents the cotylea dons; b and c, the embryo; d, shows the petioles or stems of the cotyledons.

Cotyledons, (from a Greek word, kotule, a cavity,) are the thick, fleshy lobes of seeds, which contain the embryo. In beans they grow out of the ground in the form of two large leaves. They are the first visible leaves in all seeds, often fleshy and spongy, of a succulent and nourishing substance, which serves for the food of the embryo at the moment of its germinating. Nature seems to have provided the cotyledons to nourish the plant in its tender infancy. After seeing their young charge sufficiently vigorous to sustain life without their assistance, the cotyledons in most plants wither and die. Their number varies in different plants, and there are some plants which have none.

b

Acotyledons, are those plants which have no cotyledons in their seeds; such as the cryptogamous plants, mosses, &c.

Mono-cotyledons, are such as have but one cotyledon or lobe in the seed; as the grasses, the liliaceous plants, &c.

Di-cotyledons, are such plants as have two cotyledons; they include the greatest proportion of vegetables; as the leguminous, the syngenesious, &c.

Poly-cotyledons, are those plants the seeds of which have more than two lobes; the number of these is small; the hemlock and the pine are examples.

The number of cotyledons seldom varies in the same family of plants; it has therefore been assumed by some botanists as the basis of classification; but there are difficulties attending a method wholly dependant on these organs. In order to be certain as to their number, it is necessary to examine the seed in a germinating state; this is often difficult. The natural method of Jussieu is in part founded upon the number of cotyledons.

The Embryo is the most important part of the seed; all other parts seem but subservient to this, which is the point from whence the life and organization of the future plant originate. In most dicotyledo

Albumen-Describe Fig. 110-Cotyledons-What plants are called Acotyledons? -What Monocotyledons?-What Dicotyledons ?-Polycotyledons?-Why is the number of cotyledons made the basis of classification-Embryo.

nous seeds, as the bean, orange, and apple, the embryo may be plainly discovered. Its internal structure, before it begins to vegetate, is very simple, consisting of a uniform substance, enclosed in its appropriate bark or skin. When the vital principle is excited to action, vessels are formed and parts developed which were before invisible. The embryo is usually central and enclosed by the cotyledons; sometimes it is no more than a mere point or dot, and in some cases, altogether invisible to the naked eye.

The embryo consists of the plume and radicle.

The Plume, or plumula, which is the ascending part, unfolds itself into herbage.

The Radicle, or descending part, unfolds itself into roots. At Fig. 111 appears the embryo in a germinating state; a, represents the radicle, b, the plume, c, the funicle, by means of which the plant is still connected to the cotyledons, and receives from them its nourishment.

To use the words of an ancient botanist, "the embryo continues imprisoned within its seed, and remains in a profound sleep, until awakened by germination, it meets the light and air, to grow into a plant, similar to its parent."

"Lo! on each seed, within its slender rind,
Life's golden threads in endless circles wind;
Maze within maze the lucid webs are roll'd,
And as they burst, the living flame unfold.
The pulpy acorn, ere it swells, contains
The oak's vast branches in its milky veins,
Each ravell'd bud, fine film, and fibre-line,
Traced with nice pencil on the small design.
The young Narcissus, in its bulb compressed,
Cradles a second nestling on its breast;
In whose fine arms a younger embryo lies,
Folds its thin leaves, and shuts its floret-eyes;
Grain within grain, successive harvests dwell,
And boundless forests slumber in a shell."*

There are various appendages which may or may not be present without injury to the structure of the seed.

Aigrette, or egret, sometimes called pappus, is a kind of feathery crown with which many of the compound flowers are furnished, evidently for the purpose of disseminating the seed to a considerable distance, by means of winds; as the dandelion. It includes all that remains on the top of the seed after the corolla is removed.

Stipe, is a thread connecting the egret with the seed. The egret is said to be sessile, when it has no stipe, simple when it consists

These lines, which so beautifully set forth the manner in which the embryo is contained within the seed or bulb, are not strictly philosophical, as to the fact of the future generations lying enfolded, the one within the other; it is true, that we may in many seeds, by the help of a microscope, discern the form of the future plant, but we cannot believe that this is the miniature image of another plant, which contains another, and so on through successive generations; for the fact is established, that a seed does not produce a plant without being fertilized by the pollen. We may say that a seed contains within itself the elements of future generations; but not their images, except that of the immediate plant which is to issue from the perfected seed.

What are the parts of the embryo ?-Plume-Radicle-What is the egret ?-Stipe?

of a bundle of hairs without branches, plumose when each hair has other little hairs arranged along its sides, like the beards on a feather.

Fig. 112.

In Fig. 112, a, re

Geum; e, a wing, as may be seen in the fir; fƒ, a sessile egret.

General Remarks upon Seeds.

The number of seeds in plants is variable; some have but one; some, like the umbelliferous plants, have two; some have four. The number varies from these to thousands. A stalk of Indian corn is said to have produced, in one season, two thousand seeds. A sunflower four thousand. A capsule of the poppy has been found to contain eight thousand seeds. It has been calculated that a single thistle seed will produce, at the first crop, twenty-four thousand, and at the second crop, at this rate, five hundred and seventy-six millions. In the same species of plants the number of seeds is often found to vary. The apple, and many other fruits, might be given as examples. Seeds, according as they vary in size, have been divided into four kinds; large, from the size of a walnut to that of the cocoa-nut; middle size, neither larger than a hazel nut, nor smaller than a millet seed; small, between the size of the seeds of a poppy and a bellflower; minute, like dust or powder, as in the ferns and mosses.

When a pericarp separates itself from the parent plant, or when the valves of the fruit open, the fruit has ceased to vegetate; like the leaves at the end of autumn, it has lost its vital principle, and becomes subject to the laws which govern inorganized matter.

The maturity of the seed marks the close of the life of annual plants, and the suspension of vegetation in woody and perennial ones. Nature, in favouring by various means the dispersion of these seeds, presents phenomena worthy of our admiration, and these means are as varied as the species of seeds which are spread over the surface of the earth.

The air, winds, rivers, seas, and animals, transport seeds and disperse them in every direction. Those which are provided with feathery crowns, or egrets, as the dandelion and thistle, or with wings, as the maple and ash, are raised into the air and even carried across the seas. Linnæus asserted that the ERIGERON canadense was introduced into Europe from America, by seeds wafted across the Atlantic Ocean. "The seeds," says he, "embark upon the rivers which descend from the highest mountains of Lapland, and arrive at the middle of the plains, and the coasts of the seas. The ocean has thrown, even upon the coasts of Norway, the nuts of the mahogany, and the fruit of the cocoanut-tree, borne on its waves from the far distant, tropical regions; and this wonderful voyage has been performed without injury to the vital energy of the seeds."

Number of the seeds variable-Size variable-Separation of the pericarp from the plant-What is denoted by the maturity of the seed ?-Dispersion of seeds, how effected?--Seeds carried by water.

Some fruits, endowed with elasticity, throw their seeds to a considerable distance. In the oat, and in the greater number of ferns, this elasticity is in the calyx. In the Impatiens, wild cucumber, and many other plants, it resides in the capsule. The pericarp of the IMPATIENS* upon being touched, when the seeds are ripe, suddenly folds itself in a spiral form, and, by means of its elastic property, throws out its seeds.

Animals perform their part in this economy of nature. Squirrels carry nuts into holes in the earth. The Indians had a tradition, that these animals planted all the timber of the country. Animals also contribute to the distribution of seeds by conveying them in their wool, fur, or feathers.

Although distance, chains of mountains, rivers, and even seas, do not present obstacles sufficient to prevent the dispersion of plants, climate forms an eternal barrier which they cannot pass. It is not unlikely, that in future times the greater part of vegetable tribes which grow between the same parallels of latitude, may be common to the countries lying between them; this may be the result of the industry of man, aided by the efficient means which nature takes to promote the same object in the dissemination of seeds; but no human power can ever cause to grow within the polar circles, the vegetables of the tropics, or those of the poles at the equator. Nature is here stronger than art. That something may be done to promote the growth of tropical plants in our climate is true, but how different are they with us, from the same species in their own genial climate; we toil and watch for years to nurture an orange or lemon tree, which after all is stinted in its growth, while in its own native home the same plant would have grown spontaneously in luxuriant beauty.

The diffusion of seeds completes the circles of vegetation, and closes the scene of vegetable life. The shrubs and trees are despoiled of their foliage, the withered herbs decompose, and restore to the earth the elements which they have drawn from its bosom. The earth, stripped of its beauty, seems sinking into old age ;-but, although the processes of nature may have been unseen and unmarked by man, innumerable germs have been formed, which wait but the favourable warmth to decorate with new brilliancy this terrestrial scene.

So fruitful is nature, that a surface a thousand times more extended than that of our globe, would not be sufficient for the vegetables which the seeds of one single year would produce, if all should be developed; but great quantities are eaten by men and animals, or left to perish in unfavourable situations. Some are carried into the clefts of rocks, or buried beneath the ruins of vegetables; here, protected from the cold, they remain inactive during the winter season, and germinate as soon as the early warmth of spring is felt. Then the pious botanist, beholding the vegetable species with which the earth begins to be clothed, and seeing successively all the types or representations of past generations of plants, admires the power of the Author of nature, and the immutability of His laws.

In concluding our examination of the external organs of plants, we will give a synoposis of the principal ones, with their subdivisions, as heretofore explained.

* The IMPATIENS of the garden is sometimes called Ladies'-slipper, sometimes Bal.

samine.

Elasticity of some fruits-Agency of animals-Effect of climate upon the dispersion of plants-Circle of vegetation completed-Concluding remarks.

PHYSIOLOGICAL VIEWS-GERMINATION OF THE SEED.

WE have traced the various organs of the plant, through their successive stages of development, from the root to the bud, leaf, and flower, and from the flower to the fruit and seed. We have seen, in imagination, the vegetable world fading under a change of temperature, the "sear and yellow leaf" becoming a prey to the autumnal blasts, and even the fruits themselves exhibiting a mass of decayed matter. Were this appearance of decay and death now presented to us for the first time, how gloomy would be the prospect! How little should we expect the return of life, and beauty, and fragrance! No power short of Omnipotence, could effect this; it is indeed a miracle! But we are so accustomed to these changes, that, "seeing, we perceive not;" we think not of the mighty Being who produces them; we call them the operations of nature; but what is

Enumerate the organs of nutrition-Of reproduction-What are the parts of the root?-The Stem-Bud-Leaf-Different kinds of Appendages--Divisions of the calyx-Corolla-Nectary--Stamens-Pistil-What are the parts of the fruit?--What are the parts of the pericarp ?-Parts of the seed-Of the Embryo-What remarks commence this lecture?