Plants (Nourishment Of). Plants are not so much nourished by their roots as many persons suppose; indeed, many plants are rootless. The leaves, and the soft green covering of the stem, perform a much more important part in supplying the plant with food. Plants grow by the absorption of water and the fixation of carbon - of carbon and water plants are almost entirely composed ; and unless these two substances are supplied, the plant will die. The leaves are the principal agents in the absorption and decomposition of carbonic acid and the retention of carbon, as a very simple experiment will prove. Gather a sprig of any succulent plant, and keep it in a dark place, while you prepare the materials for your experiment. Fill a tumbler glass three parts full of clear water, and with a clean tobacco pipe breathe carbonic acid gas through it for four or five minutes at least; then fill up the glass carefully, without wetting the edges, and drop in the sprig you have gathered. The glass should be so full as to make the water stand a little above the edges. A flat piece of writing paper having been laid upon the top, and aflat plate above that, the whole 6hould be turned up-side down, as in the figure. If you now place your apparatus in the sunshine, you will see small bubbles form upon the leaves of the sprig, and rise to the upper part of the inside of the tumbler; this is pure oxygen gas. The carbonic acid, which the water absorbed, is undergoing decomposition ; that is, the materials, oxygen and carbon, of which it is composed, are being separated or de-composed ; the oxygen is set free, and the sprig having used the carbon would be found to be exactly so much heavier, in proportion to the oxygen set at liberty. This operation requires light, and in a natural condition only goes on during the clay. This should be borne in mind with regard to flowers in sick rooms; in the day their presence has a purifying effect, but at night this ceases. Besides this chemical change, the leaves of plants take an active part in the function of per-spiration while exposed to sunshine. The similarity between this function in plants and animals is singular. The quantity of water thrown out by plants may be proved by the simple experiment of placing a tumbler inverted: upon the grass-plot on a fine sunn day. The sides of the glass will presently be covered with the condensed vapour of water, then drops will form, and presently run down in little streams. This fluid has, in most cases, been derived from the root. The nutritious fluid of the plant, like the blood of animals, needs exposure to the air before it is fit to take a place in the organized tissue of the body . and this contact with air is brought about in the loaf, the anatomy of which I will now endeavour to make plain to you. If you split a stem down carefully, exactly at the point where a leaf is attached, you will be able in many instances without a magnifying glass to detect that the stalk of the leaf is connected with the central pith or medulla. A leaf is composed of four layers of tissue, or two layers folded upon themselves, as these pieces of paper are folded. The outside represents the skin, or cuticle, of the stem, which is continued from the stem first along the upper surface, then turned over the edge, and so along the under surface to the stem again. This skin is colourless, or nearly so ; and like our own,- filled with pores. Viewed beneath a powerful magnifying glass, it is found to be composed of very small bags, or cells, pressed very closely together : hence it is said to be composed of cellular tissue. Our own bodies are chiefly composed of this tissue, and all growth is effected by means of the addition of these little cells. The skin, or cuticle of the leaf, is composed of compressed, or condensed, cellular tissue. Beneath it run the vessels which bring the sap up from the root, which, coming from the medulla, or pith, pass first over the upper surface of the leaf, and then, having been turned under towards the stem, deposit the new wood within the bark. Here we find, under the microscope, beautiful vessels with twisted or spiral fibres within them. These tubes are called spiral vessels, and are the agents in bringing about that wonderful change before spoken of. All the juices of plants are the same, till they pass along these vessels in the leaf, where they undergo a change. After having been exposed to light and air, in the myriads of vessels which run along the leaf, the juice, passing downwards on the outside of the stem, deposits woody fibre in its downward course. This is Chiefly composed of the carbon of the air, which has been taken from the air by the leaves, which have really much more to do with the nourishment of most plants than their roots. Here is a strong bough in the hedge, round which a piece of woodbine has been tightly bound, and which will illus-trate this matter. The stem is swelled above the mood-bine, not below, proving that the growth of the tree takes place from above downwards. You may prove this also by a simple experiment, in which a piece of" strong string may be substituted for the woodbine : - If round the stem of some rapidly-growing young tree you tie a piece of string, you will find, in a short time, that the fibres sent down from the leaves and buds will swell the stem above the ligature, while the portion of the stem below where you have tied the string will not have increased in size. Never, therefore, pluck the leaves from plants, with the idea that they have got more than their roots can nourish; for, on the contrary, the leaves are the support of the plant. The beautiful green colour of leaves depends upon the decomposition of carbonic acid in its vessels, and what we are breathing out of our lungs to-day will probably be incorporated with the tissues of a beautiful plant to-morrow ; perhaps with some blade of grass ; on that grass the cow will feed, and again appropriate the carbon, by absorbing it into its circulation, and forming the butter of milk; and of that butter, whose chief component part you breathed out from your lungs a week before, you may eat, digest, and again breathe out into the atmosphere. Such are the wonderful jour-neys of a particle of carbon.

Nourishment Of Plants 250Nourishment Of Plants 251Nourishment Of Plants 252Nourishment Of Plants 253Nourishment Of Plants 254Nourishment Of Plants 255