Sprouting of the Plant, or Germination.

When the seed is sown, and is subjected to the influence of moisture and a certain temperature, the embryo or young plant contained in it begins to sprout or germinate. The little root (r, Fig. 2, p. 211) begins to project through a hole in the seed, and elongates so as to enter into the soil for the purpose of drawing nourishment for the plant. The cotyledons then either rise above the soil, as in the lupin and the common turnip, or they remain below ground, as in the common bean or pea. In the former case the cotyledons assume a green colour, and serve the purpose

of temporary leaves until the proper foliar or leafy organs are developed; in the latter case the nourishing matter contained in the cotyledons is gradually absorbed by the plant, and they shrivel up and finally disappear. If a bean-plant is pulled up some time after it has sprouted, the two cotyledons will be seen in a withered state at the bottom of the stalk. The germination of the plant is represented in Figs. 6, 7, and 8. In Fig. 6, we observe a French bean or haricot sprouting. In this case the

1 Latin word germinare, to sprout.

2 (Fig. 6.) Haricot or French bean germinating. A dicotyledonous plant.

3 (Fig. 7.) Maize or Indian corn germinating. A monocotyledonous plant.
4 (Fig. 8.) Spore of an acotyledonous plant germinating.

9 g. corn.

little roots, coming off from the common axis t, descend into the ground; the axis ascends, bearing the two cotyledons c c, which serve a temporary purpose as seed-leaves; while from between the cotyledons rises the first stem-bud, bearing the proper leaves In Fig. 7, we notice the sprouting of the maize or Indian Here the common axis t, gives off the roots at the lower end, a single cotyledon c, and a stem-bud with ordinary leaves g. In Fig. 8, the spore or germ of an acotyledonous plant is represented giving off root-like filaments or threads r r, but having no cotyledons. The separate nutriment stored up in some seeds (Figs. 2, p. 211, 4, p. 212), is in the same way absorbed. This nutriment consists of certain organic substances, such as starch and gluten, the former of which may be resolved into carbon (C), oxygen (O), and hydrogen (H); and the latter into carbon, oxygen, hydrogen, nitrogen (N), and sulphur (S). The ascending axis or stem (g, Fig. 6, p. 213), makes its appearance after the cotyledons. It rises into the air and bears buds which produce leaves.

The Root or the descending axis of the Plant.

The root is the axis which descends into the earth, and draws nourishment from the soil. It imbibes substances in solution by means of its extremities. These consist of minute bags called cells, which absorb fluid matters, and convey them upwards to the stem (Fig. 9). As plants have no power of locomotion, their food must be placed near them. Consequently they have all the materials required for their growth in the air and in the soil; the leaves being put into relation with the former, and the roots, with the latter. The gaseous and fluid matters of the atmosphere and earth are thus converted, by the agency of plants, into the solid herbage on which animals feed, and the nutritious matter of the cereal grains

1 (Fig. 9.) Section of the end of a root highly magnified. The extreme point sp, consists of cells which are very delicate, and easily imbibe fluids; these are connected with other cells c c, and finally with tubes and vessels.

The ends of the roots

which in part constitute the food of man. ire, as it were, little mouths, which are constantly extending through the soil in quest of food. A beautiful provision is made for this by the increase taking place always at the points, and thus, the delicate rootlets are enabled to accommodate themselves to all kinds of soil. The spreading of the roots and branches also bear a relation to each other, so that the rain dropping from the ends of the latter falls over the part of the ground where the absorbing parts of the roots are situated. These interesting phenomena display the wondrous providence of the all-wise Creator.

As the roots imbibe nourishing substances from the earth, it follows that they must by degrees exhaust the soil, and unless a renewal took place the plants would die. To provide against this, the rain, the atmosphere, and the sun, are constantly acting on the soil, and causing changes, which give rise to the production of additional nourishing matters. When man wishes to get a large supply of food in a short time he applies manures, and raises his crops by rotation, so as to secure the greatest amount of produce which the plants can yield. In some plants the roots, in place of descending directly into the soil, appear first in the air and then reach the earth. This is particularly seen in the banyan and other trees of the fig tribe, also in the screw-pines and mangroves. Occasionally, as in orchids of warm countries, the roots embrace other plants and never touch the ground. Some plants send their roots into the stems or roots of other plants, and derive their nourishment from them, as may be seen in the mistletoe, the dodder, and the broom-rape. These are true parasites.

The Stem or ascending axis of the Plant.

The stem usually rises into the air and bears leaf-buds. Sometimes it creeps along the surface of the ground, as in the iris, or it remains entirely underground, as in the asparagus, Solomon'sseal, and the banana. The characteristic of the stem is the provision made for the production of leaf-buds. The eyes of the potato are leaf-buds, and hence it is a kind of underground stem. The bulbs of lilies are underground buds, developed on underground stems, with the roots proceeding from their lower part. What are called the roots of tulips and crocuses are also subterranean thickened stems, producing buds at the upper part and roots

below. While the root may be called the system connected with the soil and darkness, the stem may be said to be the system connected with air and light; it produces the leaves, and exposes them to those influences which are required for the preparation of the sap and the formation of various secretions, such as woody matter, starch, &c. The stem consists of cells, or small bladders, of various forms (Fig. 10), and of tubes, which usually

taper towards each end, and are called vessels. These vessels are either hard and firm, as in the woody tubes (Fig. 11), or they are delicate, as in spiral and other tubes (Fig. 12), in which a

1 (Fig. 10.) Cells united, and forming cellular tissue. The cells in this case are six-sided, like those of the honeycomb. They are little six-sided bags, as it were, containing various kinds of matter, according to circumstances.

2 (Fig. 11.) Woody tubes overlapping each other, and constituting woody tissue. The tubes are spindle-shaped, that is, they taper at each end.

3 (Fig. 12.) Spiral vessels, with a fibre coiled up in their interior, in a corkscrew-like

manner.

4 (Fig. 13.) Transverse section of the exogenous stem of an oak, showing cellular pith in the centre, six woody layers, forming consecutive circles round the pith, and the layers of bark outside. Immediately surrounding the pith spiral vessels occur, and the woody layers consist of woody tubes and of large vessels, having round markings on their walls, and hence called dotted or pitted vessels. The inner bark consists of woody tubes, the outer of cells. The pith and bark are united by various cellular rays.

thread is coiled up in the interior, in a more or less complete corkscrew like manner. In our ordinary trees the cells are found in the outer bark, in the pith, and in the rays which connect them ; the woody tubes occur in the inner bark and in the proper wood of the stem; and the spiral vessels in the part immediately surrounding the pith. By means of the structure of the stem the whole vegetable kingdom is divided again into three great classes, viz. : 1. Exogenous plants, in which there is a distinct separable bark and a pith, and in which the woody layers are developed in an outward direction, one over the other: this is seen in the common forest trees of Britain (Fig. 13). 2. Endogenous plants, in which there is

no separable bark and no pith; the bundles of vessels are seen in the midst of a quantity of cellular tissue, and the additions are chiefly made towards the inside, as may be seen in palms (Fig. 14). 3. Acrogenous plants, in which there is no separable bark nor pith; the vascular bundles have a peculiar irregular form, and the additions are chiefly made to the summit, as in ferns (Fig. 15). These divisions correspond with those already mentioned as founded on the embryo. Thus dicotyledonous plants have exogenous stems; monocotyledonous plants have endogenous stems; and acotyledonous plants have acrogenous stems. In some instances, plants produce mere expansions, composed of cells without any

1 From two Greek words, exo, outwardly, and gennaein, to produce.

2 Endon, inwardly.

3 (Fig. 14.) Transverse section of the endogenous stem of a palm, showing cellular tissue m, and bundles of vessels f, scattered through it. The whole is enveloped by an outer covering, which is closely incorporated with the parts below.

4 (Fig. 15.) Transverse section of the acrogenous stem of a tree-fern, showing cellular tissue in the centre m, and in the circumference p, with peculiar vascular bundles ƒ v, and the bases of the leaves forming a sort of bark c.

5 Acra, summit.