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PLANTS, THE LUNGS OF CITIES.
1. PUBLIC Squares and spacious streets, well set with trees, have been aptly1 called the lungs of cities. It is certain that the two great organized kingdoms of nature-the animal and vegetable-are designed to co-operate in their mutual development.3 The beautiful Persian fable, which describes the rose and the nightingale as shut up in a crystal cage, and mutually giving life to each other, though not strictly correct as to the action of the flower, is forcibly illustrative of the relative actions of animal and vegetable life.
2. In modern aquaria the theory becomes reality, for aquatic plants keep the water in which they grow in a fit state to sustain animal life. It is a fact well known that fishes do not thrive well in reservoirs5 destitute of aquatic vegetation. The water of an aquarium need not be changed for weeks or months, if there is a proper proportion of such plants as grow in water. This, then, is the great secret of the aquarium: the plants afford a supply of oxygen to the animals, while the animals supply the plants with the carbon which is indispensable to their growth.
3. So in the atmosphere. In large cities, where carbonic acid gas is produced in large quantities from the lungs of multitudes of people, and from the great number of fires kept constantly burning, trees act as purifiers, by absorbing the carbonic acid which is poisonous to man, and by restoring to the air the life-supporting oxygen. Throughout all portions of the globe this principle is in constant operation, evincing" the wisdom and goodness of the Deity in thus beautifully harmonizing the operations of Nature.
1 APT-LY, properly; fitly.
2 CO-OP-ER-ATE, act together.
3 DE-VEL-OP-MENT, growth; progress to higher forms.
15 RES-ER-VOIR (rez-er-vwor'), a place where water is kept in store for fountains, etc. IN-DIS-PEN-SA-BLE, absolutely necessary. 7 E-VIN'-CING, showing; making plain. A-QUÃ'-RI-A (the plural of aquarium), little 8 HÄR'-MO-NI-ZING, causing to agree. ponds, or vessels, for rearing water plants with water animals.
1. A BUD has been called a repetition of the plant on which it grows. It is common to give the name bud to that scaly envelope1 which contains the rudiments2 of a new plant; but such scales are not required to form a bud, except in cold climates.
2. The first appearance of a young branch or flower is the bud, and a new and independent plant is contained in it, as much as in a seed. Buds not only terminate growing branches, but appear in what are termed axils, or the acute angles formed by the leaves and the stem. From the buds spring branches, which are in all respects like the main stem, and which present an arrangement similar to the leaves.
3. Many buds are never fully developed, but seem to have been produced as a resource in case of the destruction of any. Thus, if the terminals bud be destroyed, lateral buds, that otherwise would have remained undeveloped, put forth shoots, and the growth of the plant is scarcely checked. It is on this principle that hedges are thickened by trimming off the tops, a process well known to gardeners.
4. Irregular buds often appear in stems gorged' with sap. The rich and much admired grain known as bird's-eye maple is attributed to the numerous buds which have appeared from time to time during the growth of the tree. Frequently two buds appear, side by side, instead of one, owing to an excess of nutritious sap.
5. Thorns are supposed to result from an imperfect growth of what should have been branches or stems. It is well known that many plants, which in a wild state abound in thorns, become free from them by cultivation. In such cases
the increased supply of nourishment afforded the plant by better tillage enables the buds to become branches instead of thorns. Thorns are of woody structure, and grow from the branch or stem; while prickles only grow from the bark, and may be peeled off with it, as will appear by stripping the bark from a rose-bush.
6. It should be mentioned here that, as a leaf-bud is really a separate and complete plant in itself—like the parent plant on which it grows if the leaf-bud can be transferred to another plant, and made to take root in and grow upon it, it will produce a stem having the same qualities as the parent plant from which it was taken. Thus, if a leaf-bud from a greening apple-tree be transferred to another tree, and made to grow upon it, it will produce the same kind of apples as its parent stem.
7. But if the secd of a greening apple be planted, and grow and produce fruit, it will, indeed, bear apples, but it is uncertain what kind of apple; it may be sweet or sour, a russet or a pippin, or perhaps some new kind not before known. It is from seeds alone that new kinds can be produced. But if any particular kind of plant is to be multiplied,1o it can only be done by aid of its leaf-buds—by planting the stems which spring from them, or by the common gardening operations of budding and grafting.
8. It is only plants whose fruit is of a like general character that can be mutually transferred in this way. The buds of the pear, the crab-apple, the common apple, and the quince, can be made to grow each upon the others; but an apple will not grow upon a peach-tree or a cherry-tree. The process of budding and grafting was known and practiced as long ago as the days of Virgil.
But various are the ways to change the state
1. THE laws by which leaves are arranged on the stem apply also to the arrangement of branches and thorns, as the latter arise from buds in the axils1 of the leaves. This is one of the most interesting divisions of Botany, especially when the very law that regulates the position of leaves, twigs, and branches is found to prevail in the arrangement and revolutions of the planetary worlds, thus plainly indicating that the same Being who clothed the lilies of the field in beauty surpassing the regal2 splendor of Solomon, "made the stars also."
2. In the arrangement of leaves even mathematical precision is manifest. Observe the leaves of grass, how one is over one side of the stem, and the next on the opposite side, while the third comes directly over the first, and the fourth over the second. When each leaf is thus one half way round, the arrangement is called alternate. In sedges, and in that pest3 of farmers and gardeners called nut-grass, each leaf is one third the way round the stem from the one below it.
3. Cherry and apple trees have the leaves and twigs two
fifths of the way round, reckoning from any leaf to the one above it—that is, five leaves appear in a spiral of two revolutions round the stem, and the sixth leaf, which is exactly above the first, commences a new series. In the holly, and a large number of trees, it may be seen that from one leaf to another directly above there are eight spaces between leaves, and that a spiral line passing through the bases of the leaf-stems will make just three turns. In this arrangement the leaves are three eighths of the circumference of the stem from each other.
4. In wormwood the leaves are five thirteenths of the circumference apart; in cones of some species of pine-trees twenty-one leaves are found in a spiral of eight turns, while in others the leaf distances are thirteen thirty-fourths of the circumference. With a few exceptions, which perhaps may have arisen from the failure of some leaf-germs to be developed, the leaves of each species of plant are arranged at regular distances from each other around the stem, although these distances vary in different species. Even in fruits, as in the protuberances of the pine-apple, this beautiful order is apparent. The plan seems to have been, amid great diversity' of position, to give to each leaf its proper share of air and light, which would not have been attained by a miscellaneous arrangement.
5. It thus appears that the leaves of plants do not take positions as if by chance, starting out here and there at random, but, making their appearance in the lines of regular revolving spirals, they obey definite laws in their arrangement. What is still more curious, a law in all respects similar appears to extend to the solar system itself, and to govern the revolutions of the heavenly bodies; for the same numbers that express the relative distances in the arrangement of leaves of different species around their central stem, denote very nearly the relative times of the revolutions of the planetary worlds around their central sun.
Arrangement of the Leaves
of the Cherry.