that creep through the earth seeking food for the tree. Some, as in the spruce or hemlock, do not go very deep but spread great distances through the soil in search of food, others, like the hickory, go nearly straight down. The interesting feature of these tree roots is that the part nearest the trunk is all but dead, and acts mostly as an anchor, while the fibrous rootlets or even finer subdivisions known as _root hairs_ at the extremities are the food gatherers. At the very end of all rootlets and of roots is a _rootcap_ (Figure 3), harder than the rest of the threadlike rootlet. This rootcap is, if not quite dead, at least useless as a food gatherer, but serves as a tiny pioneer wedge which forces its way among stones or other obstructions, so allowing the living root hairs just behind to gather the food to which it leads the way. In certain of the rocky islands of the Bahamas wild fig trees may be seen, growing on the bare rocks, their roots sprawling in every direction in search of a crevice through which the rootcap can force its way. Such roots may extend thirty or forty feet from the trunk of the tree over the bare rock in search of a favorable crack where they plunge to the cool depths and secure the food and water necessary for life. [Illustration: FIG. 3.--TAP ROOT OF SEEDLING The figure shows the root cap at the extremity.] Roots are not always of this common type. Sometimes, particularly in certain biennials, they are swelled to form great thickened portions, often weighing many pounds. The sweet potato is a familiar example, and a related plant, one of our morning-glories, has an enormous perennial root, known to weigh as much as fifty pounds. This swelling of the roots of plants is a quite common characteristic of certain kinds and has great commercial significance. Carrots, turnips, rutabagas, beets, and parsnips are familiar examples. The purpose of such roots is to store food for the plant, and this thrifty habit of some roots has been turned by the gardeners to our advantage. It is a common sight to see parts of a sidewalk heaved up by a tree root and their force in this respect is tremendous. One of our common ferns has been known to raise a weight of over 500 pounds, and even to break through a concrete walk. Such is the force exerted by the roots of plants that we can truly think of roots as pushing through the earth almost regardless of obstacles, binding the soil together and not only serving the needs of the plants, but actually holding the soil on steep slopes. Where fire or ruthless lumbering has stopped this natural process the washing away of the soil and exposure of the bare rocks leaves desolation behind it. [Illustration: FIG. 4.--ADVENTITIOUS ROOTS OF THE TOMATO Produced from joints or injured places.]