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or hair-like egret; þ the plumose, or feathery egret; c and d show the style remaining, and forming a train as in the virgin's bower and geum; e a wing, as may be seen in the fir; and f a sessile egret.
General Remarks upon Seeds. The number of seeds in different plants is variable; some have but one; some, like the umbelliferous plants, have two; some have four, as in the rough leaved plants ; in the order Gynospermia, of the class Didynamia, there are four lying naked in each calyx. 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 others 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 hazle nut, nor smaller than a millet seed; small, between the size of the seeds of a poppy and a beil flower; 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, this is not the effect of vital activity, but a proof that the fruit has ceased to vegetate. The fruit, like the leaves at the end of autumn, losing the vital principle, is submitted to the laws which govern inorganized matter.
The period in which the seeds arrive at maturity, marks the period of the life of annual plants, and the suspension of vege. tation in woody and perennial plants. Nature, in favouring by various means, the dispersion of these seeds, presents pheno.
Number of seeds variable-Size variable-Separation of the pericarp from the plant.
mena worthy of our admiration, and these means are as varied as the species of seeds which are spread upon the surface of the earth.
The air, winds, rivers, seas, and animals, transport seeds and disperse them in every direction. Seeds provided with feathery crowns, (egrets,) as the dandelion and thistle; with wings, as the maple and ash, are raised into the air and even carried across
Linnæus asserted that the ERIGERON canadense was introduced into Europe from America, by seeds wafted across the Atlantic Ocean. • The seeds,” says Lin. næus, “embark upon the rivers which descend from the high. est 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 cocoa nut 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
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, in the cucumber, (Cucumis,) and many others, it resides in the capsule. The pericarp of the IMPATIENS, (sometimes called touch-me-not, and jewel-weed,) consists of one cell with five divisions; each of which, when the seeds are ripe, upon being touched, suddenly folds itself in a spiral form, leaps from the stem, and, by means of its elastic property, scatters its seeds to a great distance.
Animals also perform their part in the diffusion of seeds. Squirrels and other animals carry seeds and nuts into holes in the earth. The Indians believed that the squirrels planted all the timber of the country; there is no doubt but that they do much towards diffusing different kinds of nuts and seeds; as chesnut, oak, walnut, &c. Animals 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 disper. sion of vegetables, climate fixes an eternal barrier which plants
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 all countries of that zone ; this may be the result of the industry of man, aided by the ef. ficient means which nature takes to promote the same object in the dissemination of seeds; but no human power can ever
Dispersion of seeds, how effected ?-Seeds with egrets, and wings--Seeds carried by water - Elasticity-Agency of animals-Effect of climate upon the dispersion of seeds.
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 man. That something may be done by art to. promote the growth of the tropical plants in our climate is true, but how different are the same plants with us, from what they are 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 it would have grown spontaneously in luxuriant beauty.
The diffusion of seeds completes the circle of vegetation, and closes the scene of vegetable life. The shrubs and trees have lost 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 unseen by us, and unmarked the processes of nature by too many among men, innumerable germs have been formed, which wait but the favorable warmth to dec. orate with new brilliancy this terrestrial scene.
So fruitful is nature, that a surface a thousand times more ex. tended than that of our globe, would not be sufficient for the ve. getables which the seeds of one single year would produce, ifall should be developed ; but the destruction of seeds is very great, great quantities being eaten by man and beast, and left to perish in unfavourable situations. Those which are preserved, con. stitute but a small proportion of the whole; they are either carried into the clefts of rocks, or buried beneath the ruins of ve. getables ; 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 botanist who considers with a curi. ous eye, the vegetable species with which the earth begins to be clothed, 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.
We have now considered the various organs of plants, we have traced them through their successive stages of developement, from the root to the bud, leaf, and flower, and from the flower to the fruit and seed. We have seen, in imagination,
Circle of vegetation completed-concluding remarks-Com Acement of Lecture XVI.
the vegetable world, fading under a change of temperature, the “ sear and yellow leaf,” 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, can effect this miracle! But we are now so accustomed to these changes, that, “ seeing, we perceive not;" we think not of the mighty Being, who produ. ces them ; we call them the operations of nature ; and what is nature, or what are the laws of nature, but manifesta. tions of Almighty power?
The word nature, in its original sense, signifies born or pro. duced ; let us then look on nature as a created thing, and be. ware of yielding that homage to the creature which is due to the Creator. The sceptic, with seeming rapture, may talk of the beauties of nature, but cold and insensible must be that heart, which from the contemplation of the earth around, and the heavens above, soars not to Him,
“ The mighty Power from whom these wonders are.” How beautifully is the reanimation of the vegetable world, brought by St. Paul, as an illustration of our resurrection from the dead! The same power, which from a small, dry, and apparently dead seed, can bring forth a fresh and beautiful plant, can also, from the ruins of our mortal bodies, produce a new and glorious body, and unite it to the immortal spirit by ties never to be separated.
Germination. The process of the shooting forth of the seed is termed germination. The principle of life contained in the seed does not usually become active, until the seed is placed in circumstances favourable to vegetation. When a seed is com. mitted to the bosom of the earth, its various parts soon begin to dilate by absorbing moisture. A chemical action then commences ; oxygen from the air unites to the carbon of the seed and carries it off in the form of carbonic acid gas. As the car. bon of the cotyledons by the process continues to diminish, and oxygen is produced in excess, a sweet, sugar-like substance is formed; this is conveyed to the embryo, which by its new nourishment is kindled into active life ; from this period we may date the existence of the young plant.
Cause of our forgetfulness of God when beholding his operations- Meaning of the word nature - Feelings which should be excited by created objects—Si. Paul's illustration of the resurrection-Describe the process of germination,
Bursting through the coats which surrounded it, and which are already enfeebled by their loss of carbon, the embryoemerges from its prison, the radicle shoots downward,
and the plume rises up6
wards. We say then that the seed has come up or sprouted. Fig. 88 represents a young dicotyle. donous plant, with its radicle, , developed; its plume, b, is yet scarcely perceptible its cotyledons, c, appear in the form of large, succulent seed-leaves. The radi. cle, or descending root,
is usually the first to break through the coats of the seeds; it commences its journey downwards, to seek in the earth nourishment for the future plant, and to fix it firmly in the earth. This constitutes the root, and always takes a downward course, in whatever situation the seed may have been placed in the ground.
A botanist once planted in a pot, six acorns, with the points of their embryos upwards. At the end of two months, upon removing the earth, he found that all the radicles had made an angle in order to reach downwards. It is supposed that if the root met with no obstruction in going downwards, it would always be perfectly straight. Fig. 89.
Fig. 89 is the representation of a germinating seed of the mirabalis (four o'clock); it will be seen that the radicle, a, has made nearly a right angle in turning downwards; the plume is not developed.
If you put cotton into a tumbler of water, and place upon it some seeds
of rye or wheat, which soon vegetate, you will see all the fibres shooting from the seeds, in a perpendicular direction, downwards. It is a very simple and
Experiment with acorns – Explanation of Fig. 89—Seeds placed on cotton in a tumbler.