These experiments, says Chaptal, leave little if any doubt, but that vegetables derive the earthy matter they contain from the soil in which they grow.[13]
2. Of water, as an agent in vegetation.
Seeds placed in the earth, and in a temperature above the freezing point, and watered, will develope; that is, their lobes[14] will swell, their roots descend into the earth, and their stems rise into the air. But without humidity, they will not germinate; or deprived of humidity after germinating, they will perish. When germination is complete, and the plant formed, its roots and leaves are so organized as to absorb water. The experiments of Hales prove, that the weight of plants is increased in wet and diminished in dry weather; and that in the latter, they draw from the atmosphere (by means of their leaves)[15] the moisture necessary to their well being.—Du Hamel (and after him Sennebier) has shown, that the filaments that surround the roots of plants, and which has been called their hair, perform for them in the earth, the office that leaves perform in the atmosphere, and that if deprived of these filaments the plants die.
It would be easy, but useless, to multiply facts of this kind tending to establish a doctrine not contested, but which after all does not assert, that water makes part of the food of plants. On this point two opinions exist—the one, that this liquid is a solvent and conductor of alimentary juices: the other, that is itself an aliment and purveyor of vegetable food at the same time. The first opinion is abundantly established. Water when charged with oxygen, supplies to germinating seeds the want of atmospheric air, and saturated with animal or vegetable matter in a state of decomposition, or slightly impregnated with carbonic acid, very perceptibly quickens and invigorates vegetation. The second opinion is favoured by some of De Saussure's experiments. On these, Chaptal makes the following remark, which expresses very distinctly an approbation of the doctrine they suggest:—"The enormous quantity of hydrogen (which makes so large a part of vegetable matter) cannot be accounted for but by admitting (in the process of vegetation) the decomposition of water, of which hydrogen is the principal constituent; and that though there is nothing in the present state of our experience that directly establishes this doctrine, yet that its truth ought to be presumed, from the analysis of plants and the necessary and well-known action of water on vegetation.
(To be continued.)
Correction.—In copying the second section, page 55, an error escaped in relation to the Tuscan plough; the passage should have read thus—"The plough of the north of Europe, like that of this country, has the power of a wedge, and acts horizontally—that that of Tuscany has the same direction, but very different form. With the outline of a shovel, it consists of two inclined planes, sloping from the centre, and forms a gutter and two ridges.
Review for the Rural Magazine.
An Expose of the Causes of Intemperate Drinking, and the means by which it may be obviated. By Thomas Herttell of the city of New York. Published by order of the New York society for the promotion of internal improvement.—New York, 1819.—pp. 56.