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size, and assumes a deep red or orange color. In the one case the root is not much thicker than a common quill, in the other it becomes as thick and long as a man's arm.
1 UN-DER-GO', pass through.
2 PROD'-UCE, that which is produced.
13 A'-RE-A, extent of surface.
THE STEMS OF PLANTS.
1. THAT part of the plant which grows upward from the root becomes the stem and branches. Of all parts of the plant, it is, perhaps, the most useful to man, as it furnishes the principal materials for his dwellings, his ships, his wagons or carriages, and food for the support of animal life. Its principal use to the plant is to hold the leaves up to the air and light, and to furnish a me
Cross section of an Ex-og'-en-ous stem. dium for the circulation of the sap.
2. It has been stated that the two great divisions of flowering plants are the outward-growing, or exogenous, and the inward-growing, or endogenous. The stems of these two divisions differ widely in arrangement and appearance, as may be seen by examining the two representations of them on the next page. (See Fig. 8-9.) The exogenous plants have an outer bark, a wood, and pith; the wood is arranged in circular layers around the centre by yearly additions; and there are rays branching from the central part to the circumference. These rays add great beauty to many kinds of wood, where they are known by the name of silver grain. In maple and oak they are very conspicuous.1
Fig. 7, above, represents a cross section of an ex-o'-en-ous stem, one of the cone-bearing species 'n the eighth year of its growth, showing eight distinct zones, or layers, sur. rounding the central pith. In this specimen the markings are very distinct.
3. In the endogenous, or inward-growing stems, there are no concentric2 circles of wood; neither is there pith or bark; but bundles of woody fibres are scattered throughout the cell work. While an exogenous stem, when cut across, shows the circular layers, which represent the number of years of its growth, as in the example which we have given in Fig. 7, the endogenous stem is merely an irregular mass of cells and woody fibre.
4. The division of plants into herbs, shrubs, and trees, is based on peculiarities3 of the stem. The root of an herb may be perennial, but its stem is annual,5 and dies at the end of the first year, as we see in the hollyhock. A tree has perennial roots and stem, which are of woody fibre, with a distinct trunk or body between the roots and branches. A shrub is a small tree which sends out branches from the surface of the ground, and has no distinct trunk.
5. In the lower orders of vegetable life there is a kind of plants, most of them very small, which have neither branches nor leaves. As they are "flowerless plants," they form a
b. d. e. d. c. d. c. s.
a. 3. c. d. c. d e. d. b.
Fig. 8 represents the ex-og'-en-ous stem of the oak in the fourth year of its growth. The lower part is a vertical section, and the upper part a cross section, or horizontal section. In the horizontal section four distinct layers are seen surrounding the pith in concentric circles. The lines branching outward from the pith to the bark are the med'-ul-ry rays.
At a is shown the pith; b, the bark; c, c, c, dotted ducts; d, d, d, layers of woody Apre; 8, spiral vessels of the med'-ul-la-ry sheath.
Fig. 9 represents the en-dog'-en-ous stem of the palm, the upper part being a horizontal section, and the lower vertical. As the new growth takes place constantly from within, the vascular fibres f,f,f,f, are constantly pushed outward and compressed, and the outer part of the stem--the rind or covering-becomes the hardest, which is the reverse of what takes place in the ex-og'-en-ous, or outward-growing plants. In the en-dog'-enous stem there is no distinction of pith, wood, and bark, nor does a cross section show any concentric arrangement of annual layers.
class by themselves.* The red snow of polar regions, the green scum of stagnant water, the fungus growth on decayed wood, and various kinds of mould and mildew so common in damp places, are mostly flowerless plants. Yeast, to which we have already alluded, consists of a little cell plant of the same family. Rust and smut in grain, and dry rot in wood, are composed of similar minute plants.
6. The lowest grade of plants with stems are liverworts, which grow in wet places. Next come the mosses with stems and distinct foliage, and ferns which frequently grow several feet in height, with a peculiar stem called a stipe. Probably the highest grade of flowerless plants in this country is the scouring rush, which seems to be all stem, and entirely destitute of leaves. It grows in sandy places, and contains so much silex, or sand, that it is used for scouring and polishing articles of furniture. In ascending the scale of vegetable development we come next to grasses, sedges, rushes, lilies, flags, reeds, and palms.
7. All endogenous stems rapidly attain their full size, which seldom exceeds eighteen inches in diameter, though the height sometimes reaches one hundred and fifty feet. It is in the exogenous division of plants that the famed trees of mammoth growth are found. Pliny, an ancient writer, mentions one, in the hollow trunk of which Lucan, the Roman consul, supped and slept with twenty men. A chestnut-tree on Mount Etna is said to be sixty-four feet in diameter, and it is of such renown that it is mentioned in ancient maps of Sicily.
8. Travelers in Africa have described the gigantic baobabtrees, one of which, at the mouth of the Senegal River, is supposed to be upward of two thousand years old. On the opposite page is a drawing of it. It has a short and massive trunk, thirty feet in diameter. When seen at a distance it presents almost the appearance of a forest, and it is not till the spectator has satisfied himself by a near inspection9 that he can be convinced that the luxuriant verdure above pro
*They are called "flowerless," or eryp-tog'-a-mous plants. The latter name, which means "hidden fructification," intimates that they may have something answering to flowers and seeds, although not the same as seeds; and this is now known to be the case with most of them,
ceeds from a solitary stem. enormous tree, clothed with its brilliant verdure and snowy blossoms, must be a magnificent spectacle; and we can not wonder at the feelings which prompt the untutored10 negro to worship under its shade, and hail the opening of its flowers with pious veneration.11
9. But even the great baobab must yield in dimensions to the mammoth red-wood trees of California. One of these trees was three hundred feet in height, and thirty in diameter, and its bark was fifteen inches in thickness. When it was felled,12 the trunk was perfectly sound to the centre. The largest of the group, known as the "Father of the Forest," has long been prostrated; but it is great even in its ruins. It is estimated that it was four hundred and twenty feet in height, or only a few feet lower than the highest of the Egyptian pyramids.
10. The stems of some trees send down branches which take root in the earth and form new trunks. The most remarkable instance of a plurality of trunks is seen in the banyan-tree of India. It has at first but one stem; but from the branches leafless shoots are sent down, which, taking root, become secondary stems. This process is repeated till one tree makes a forest. There is said to be one in Hindostan with three hundred and fifty larger trunks and three thousand smaller ones, covering seven acres, and furnishing shelter for seven thousand men.
11. These magnificent natural temples are esteemed13 sacred by the Hindoos, and are dedicated14 to religious rites." Milton has beautifully described this tree:
"Branching so broad and long, that in the ground
About the mother tree, a pillar'd shade,
12. Another kind of stem, remarkable in many respects, is that of the cactus, an order of plants found almost exclusively in America, and abundant in Mexico, Oregon, and California. They are usually leafless plants, presenting their juicy stems under a great variety of forms, from that of an egg to a lofty fluted column, and, in the case of the giant cactus of California, exhibiting a leafless branching trunk fifty or sixty feet in height. Growing mostly in hot, dry, and rocky places, where they are exposed for many months in the year to the fiercest beams of a tropical sun, they are remarkably adapted, by a wise provision of Nature, to the situations in which they are destined to live.
13. During the wet season of the year they grow rapidly, and so fill themselves with nourishment that they may be literally said to gorge16 themselves with food. Then, when the rains cease, and the air becomes dry, and the spirit of the desert resumes his withering dominion over their climate,
Fig. 10, Cactus Plants. At 1 is seen the Cactus opuntia, or prickly-pear cactus, its stem and branches forming a succession of thick and flattened joints; at 5 is one similar, but with shorter and flatter joints; 2 and 4 are plants belonging to the Cereus genus of cactuses, the latter being the giant cactus of California, which rises to the height of 50 or 60 feet; 3 is the melon cactus; and 6 is the Cereus speciosissimus in full bloom.