10. But when the smoother stem from knots is free, 1 EN'-VEL-OPE, an inclosing cover. 3 DE-VEL'-OPED, unfolded; fully grown. 5 TERM'-IN-AL, growing at the end. 6 LAT'-ER-AL, growing at the side. 7 GORGED, filled; glutted. 8 NU-TRI"-TIOUS, nourishing. 9 TRANS-FERRED TO, conveyed to. 20 MUL'-TI-PLIED, increased. 11 "TO BUD," or "to IN-Oe'-U-LATE," is to 18 insert the bud of one plant or tree in or under the bark of another. FOS'-TER-PLANT'-LET," a little plant that grows on a stem that is not its parent LESSON XVI. LEAF ARRANGEMENT. 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 spiral1 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 bases5 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. Arrangement of the Leaves of the Cherry. 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. 6. Thus, regarding Neptune as the most distant of the planets, we find that Uranus, the next in order, revolves around the sun, to speak in round numbers, in one half of the time of Neptune; Saturn in one third of the time of Uranus; Jupiter in two fifths of the time of Saturn; the Asteroids, which supply the place of a missing planet, in three eighths of the time of Jupiter; and so on down to Mercury, the planet nearest the sun, whose time of revolution is not far from thirteen thirty-fourths of that of Venus, its nearest neighbor. 7. These numbers singularly correspond with those which denote the relative distances of the leaves of different species of trees, shrubs, and herbs, in their spiral revolutions around the central axis10 of their orbits.11 When we find the measures used in scanning "the plants, the poetry of earth," and "the stars, the poetry of heaven," to be the same, shall we doubt that one designer planned the whole ?* 1 Ax'-IL, the angle, on the upper side, formed by a branch with a stem or leaf. 2 RE-GAL, kingly; royal. 3 PEST, plague; any thing very troublesome. 7 DI-VERS'-I-TY, variety. 8 MIS-CEL-LA'-NE-OUS, irregular; without rule. 9 U'-RA-NUS. 10 AX-18, plural ax'-es, the central part of a stem; that around which any thing revolves. 6 PRO-TU-BER-AN-CES, the little knobs or 11 ORB'-IT, the path or track of a revolving * EXPLANATORY NOTE.-The following fractions show the distances around the stem from one leaf to another, in different species of plants: In the third fraction in the series, 2 revolutions give 5 leaves; in the fourth, 3 revolutions give 8 leaves, and so on. It will be seen that the sum of any two consecutive numerators gives the next numerator. The same is also true of the denominators. value of each fraction after the second is between 66 = and The In the adjoining table the time of revolution of the planets is given in approximate or round numbers, and also the fraction or ratio of the time of one planet to the time of the one exterior to it. It will be seen that these fractions, which nearly represent the ratio of planetary periodical revolutions, are the same as those which represent the law of Phyllotaxis, or Leaf Arrangement. The break in the series at the Earth, where the 21 ratio eight twenty-one is that of the year of Venus to the year of Mars, will be best explained in a =subsequent article on Astronomy. 1. 2. LESSON XVII. VEGETABLE REPRODUCTION.-FLOWERS. "GOD might have made the earth bring forth Enough for one and all, The oak-tree and the cedar-tree Without a flower at all. "He surely might have made enough For luxury, medicine, and toil And yet have made no flowers." 3. These verses by Mrs. Howitt are very pretty, and, in a certain sense, very true; but, while it is admitted that God might have made and propagated' the oak-tree and the cedar-tree without flowers, it is manifest2 that he has not chosen to do so. 4. We read that, by Divine command, "the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind." The organs3 especially designed to secure the multiplication or propagation of plants are the flower, fruit, and seed; and they depend on each other in the order in which they are named. 5. It is true that plants are often multiplied by separation of shoots or buds, which, being complete in themselves, constitute an individual plant. Many leaves, as those of the orange and fig, may be separated from their stems, and, if carefully placed in the earth by their petiole or leaf-stalk, will take root and produce new plants. Dahlias,5 potatoes, and tulips are propagated from tubers or bulbs; roses, vines, etc., by cuttings or slips placed in earth; and apples, pears, and quinces by grafting or budding. This is, however, rather vegetable continuation and multiplication than reproduc tion." K 6. The flower, which Pliny fancifully called "the joy of the trees," is a peculiar kind of branch, consisting of a peculiar kind of leaves; and, whatever the laws are of the arrangement of branches with respect to each other, the same will regulate the arrangement of flowers. A leaf-bud, starting in all respects apparently like its fellows, becomes changed by some cause of which we are ignorant, although supposed to be by an increased supply of nutriment, and thus what would otherwise have been a branch or a leaf becomes a flower, perhaps of exceeding beauty in coloring, fragrant in odors, and producing a fruit luscious to the taste. Similar and equally important changes, which will be hereafter noticed, take place in other departments of Natural History. 7 7. A complete flower consists of four parts, or series of organs, viz., calyx, corolla, stamens, and pistil. (See Fig. 15.) The two former are rather ornamental than essential, as a flower, botanically speaking, can consist of stamens and pistil alone. Stāmens and pistils are the essential1o organs of a flower; but sometimes there is only one of these present, the other organ being in another blossom on the same plant, as in the Indian-corn, where the ear is but half a flower, having for pistils what we commonly call the silk, while the tassel is the other half, containing the stamens. 8. This mode of flowering is seen in many forest trees, as the oak, beach, chestnut, birch, and walnut. Frequently, also, one half of the flower, or the blossom with one essential organ, is on one plant, and the other organ on another plant. Fig. 15. The several Parts of a complete Flower. Fig. 15 shows the different parts of the flower of the Evening Primrose, Enothera fruticosa. a Pe, Pe, in the drawing on the left, are the petals of the flower, within which are the stamens surrounding the St pistil. The calyx, which is at the base of the flower, has been removed, but its four sepals may be seen turned down at s, on the stem at the right. Here the petals have been removed, the better to show the stamens, st, and the pistil, Pi. The top of the pistil of this flower is divided into four narrow stigmas; but in many plants it is a mere roundish knob." The letters a a show the anthers, or knobs on the top of the stamens. At o is the o-va-ry, which contains the seed. In many plants the ovary is at the lower end of the pistil, within the petals. At ov is shown the ovary, in a more advanced state, cut across. At Pol are shown grains of pollen from the anthers, highly magnified. |