THE VEGETABLE WORLD.
We pencil a few passages, at random, from Part 14 of Knowledge for the People—(Botany, concluded.)
Why does snow, when in contact with leaves and stems, melt more speedily than when lodged upon dead substances?
Because of the internal heat of the plants, heat being a production of the vegetable as well as animal body, though in a much lower degree in the former than the latter. Mr. Hunter appears to have detected this heat by a thermometer applied in frosty weather to the internal parts of vegetables newly opened. It is evident that a certain appropriate portion of heat is a necessary stimulus to the constitution of every plant, without which its living principle is destroyed.—Smith.
Why is fructification so important to plants?
Because it continues them by seeds, and, according to Sir James Smith, "all other modes of propagation are but the extension of an individual, and, sooner or later, terminate in its total extinction." Dr. Drummond is of a contrary opinion, and quotes the following fact:—"In South America there is a species of bamboo which forms forests in the marshes of many leagues in extent, and yet Mutis, who botanized for nearly twenty years in the parts where it grows, was never able to detect the fructifications."—Humboldt.
The produce of vegetable seeds in a hundred-fold degree is common, and many trees and shrubs bring forth their fruit by thousands. A single plant of the poppy will produce above 30,000 seeds; and, of tobacco, above 40,000; and Buffon remarks, that from the seeds of a single elm-tree, one hundred thousand young elms may be raised from the product of one year. Some ferns, it is said, produce their seeds by millions.
Why should seeds be uniformly kept dry before sown?
Because the least damp will cause an attempt at vegetation, when the seeds necessarily die, as the process cannot, as they are situated, go on.
Why, in summer, is continued watering required to newly sown seeds?
Because, if the soil is only moistened at the time of sowing, it induces the projection of the radicle, or first root, which, in very parching weather, and in clayey cutting soil, withers away, and the crop is consequently lost, for want of a continued supply of moisture.
Why is selection important for procuring abundance of genuine seeds?
Because we may then choose the most vigorous plants, which naturally prove of greater fecundity. Thus, in 1823, Mr. Shirreff marked one vigorous wheat plant, near the centre of a field, which produced him 2,473 grains. These were dibbled in the autumn of the same year, the produce sown broadcast the second and third years, and the fourth harvest produced forty quarters of sound grain. A fine purple-topped Swedish turnip produced 100,296 grains, which was seed enough for five imperial acres, and thus, in three years, one turnip would produce seed enough for Great Britain for a year.—Quarterly Journal of Agriculture.
Why are winds the great agents by which seeds are diffused?
Because seeds are, as it were, provided with various wings for seizing on the breeze. The thistle and dandelion are familiar examples of this mode of dissemination. "How little," Sir J.E. Smith observes, "are children aware, as they blow away the seeds of dandelion, or stick burs in sport upon each other's clothes, that they are fulfilling one of the great ends of nature." Dr. Woodward calculates, that one seed of the common spear thistle will produce "at the first crop, twenty-four thousand, and consequently five hundred and twenty-six millions of seeds, at the second."
Some plants discharge their seeds. Thus, a certain fungus has the property of ejecting its seeds with great force and rapidity, and with a loud cracking noise, and yet it is no bigger than a pin's head!
Why is a milky fluid found in the cocoa-nut?
Because in this case, as well as in a few others, all the fluids destined to nourish the embryo of the fruit does not harden, whence a greater or less quantity of this kind of mild emulsion is contained within the kernel.
Why are certain eatable roots unfit for the table when the plants have flowered?
Because the mucus or proper juice in the tubular cells being appropriated for perfecting the flower stem, the flower, and the fruit, is absorbed as the fructification of the stem advances; and, as these are perfected, the cells are emptied, and their sides become ligneous.
Why is the Jerusalem Artichoke so called?
Because of its corruption from its Italian name, Girasole Articiocco, sunflower artichoke, as the plant was first brought from Peru to Italy, and thence propagated throughout Europe.—Smith.