7. Although no solid substance can find its way through the roots into the plant, yet as the water which the rootlets absorb from the earth always contains earthy matters, it is through this medium that the plant is nourished, when the matter in solution is such as the plant requires for its structure.10 In this way, also, the plant is poisoned when substances injurious to it are thrown around the roots; and in the same way the wood of trees designed for ornamental purposes has been dyed by chemical substances.

8. Although roots generally grow in the ground, yet some, like those of parasites11 and air-plants, grow upon other vegetables, and have no immediate connection with the soil. Nor does it follow that all subterranean12 vegetable organs are roots. The root-stalks of the sweet flag and ginger, also tubers like the common potato, artichoke, and dahlia, and the bulbs of the turnip, lily, tulip, and onion, may very properly be considered as underground stems, although, in botanical language, they are usually described as roots. (Fig. 6.)

Fig. 6.-Botanists not only give particular names to all parts of plants, but also particular terms to express their principal varieties of form. Hence, in advanced works on Botany, these terms must be defined and explained. Although, of the root, stem, and leaves, the former is the simplest, and least varied in its modifications, yet it exhibits quite a number of varieties in form, the principal of which will be described here.

At 1 is shown the sprouting of a grain or kernel of corn, sending upward a little stalk which contains a single seed-leaf, or co-tyl-e'-don, but has wrapped up in it other leaves. It has a single rootlet, or rad'-i-cle, which shoots downward. At 2 the corn plant is seen farther advanced, each leaf coming out from within the others as the plant grows. A cluster of fibrous or thread-like roots has also made its appearance.

At 3 is the seedling plant of the maple, with its pair of seed-leaves, or co-tyl-e'-dons, showing that it belongs to the class of di-co-tyl-e'-don-ous plants (see note, page 193). At 4 is a turnip-shaped or na'-pi-form root; 6, spindle-shaped, like a radish; 7, roots of the dählia, clustered and tuberous; 8, the potato, also tuberous; 9, the corm, or solid bulb of the crocus, which is merely a short and thick rootstock; 10, the scaly bulb of the lily; 11, the rhi-zō'-ma or rootstock of the Solomon's seal, properly an underground stem; 12, the strawberry, sending out runners, which take root and produce new plants.

9. Roots are classified, in respect to duration, as annual,13 biennial, and perennial. Annual roots are fibrous, 14 and produce, during their brief existence of a single season, herbage, flowers, and seeds. Biennial plants produce leaves the first year, but their flowers, fruit, and seeds appear during the second and last year of their existence. Perennial plants live through a series of years, producing leaves, flowers, and seeds during the natural period of their lives, which is sometimes reckoned by centuries.15

1 OUT'-SET, beginning.

2 IN-QUI'-RIES, questions; seeking for information.

9 "MATTER IN SOLUTION," that which is dissolved in the water.

10 STRUCT'-URE, growth or formation.

3 €ŎM'-POUND, not simple; composed of sev-11
eral parts, or of different materials.

4 FUNC'-TIONS, offices; employments.
5 GERM-I-NA-TION, the act of sprouting.
6 DOR'-MANT, in a sleeping state.

7 IN-VERT-ED, turned upside down.

PAR-A-SĪTES, plants that live and grow on other plants.

12 SUB-TER-RA'-NE-AN, being under the surface.

13 AN'-NU-AL.

AL.

BI-EN'-NI-AL.

PER-EN'-NI

8 "MAN'-TU-ÁN BÄRD," Virgil: called the 14 FI'-BROUS, having small thread-like roots. Mantuan bard because he was born near 15 CEN'-TU-RIES, hundreds of years. Mantua, in Italy.

LESSON V.

CHANGES PRODUCED BY CULTIVATION.

The po

1. THE changes which roots and tubers can be made to undergo1 are numerous and highly beneficial to man. tato, for example, is a native of tropical America, and when found wild its tubers are small and scarcely fit to be eaten, while it has been rendered by cultivation one of the most valuable articles of food. The produce2 of an acre of wild potatoes could be held in a single measure, while the same area,3 under cultivation, will sometimes yield two or three hundred bushels. Cultivation has produced a thousand varieties of this tuber, varying in shape, size, color, and quality.

2. Beets, parsnips, and turnips are also made to assume many variations under proper cultivation. The bulb of the latter, for instance, has, since the beginning of the present century, been changed from globular to spindle-shaped, in colors from white and yellow to purple and green, and in weight from a couple of ounces to twenty pounds. So also with the carrot, which in a wild state is a slender, tapering root of a yellowish-white color, but which, by cultivation, increases in

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.

CHAMBERS.

4 GLOB'-U-LAR, roundish; like a globe.

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-og'-en-ous stem, one of the cone-bearing species, in the eighth year of its growth, showing eight distinct zones, or layers, surrounding 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, 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

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'-ulla-ry rays.

At a is shown the pith; b, the bark; c, c, c, dotted ducts; d, d, d, layers of woody fibre; 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, are vegetable productions of the 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 Sicily.

of

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.