“The stalk or trunk is the upward-growing part of the plant, and needs air and light. The root, on the contrary, is the downward-growing part, and it needs soil and darkness. The extreme ends of the root’s various subdivisions are always growing, always young, of delicate structure, and for that reason admirably fitted for imbibing, very much as a fine sponge would do, the liquids with which the soil is impregnated. Because of their facility in absorbing moisture these ever-growing tip-ends are called spongioles. The spongioles terminate the rootlets, that is to say the final subdivisions of the root, subdivisions known as root-hairs on account of their resemblance to real hair. “The root takes various forms, which are all reducible to two fundamental types. Sometimes it consists of a main body or tap-root, which sends out branches as it bores deeper into the soil. This designation, tap-root, is a common and familiar term. Sometimes the root assumes the form of a tuft, a bunch of rootlets, simple or branching, which, springing from the same point, continue to grow at a nearly equal rate and on an equal footing as to importance. Roots of this sort are commonly known as fibrous roots. “As a general rule, the growth of the root keeps pace with that of the stem or trunk. Thus the oak, elm, maple, beech, and all our large trees have a vigorous, deep-growing root as anchorage for the enormous superstructure, to brace it firmly against the wind. But there is no lack of lowly herbage that has roots quite out of proportion to the other parts,—veritable tap-roots of greater size and vigor than many a plant of far greater aërial development can boast. To this class belong the mallow, carrot, and radish. Lucerne has for support to its meager foliage a root that bores two or three meters into the ground.