layers of wood which appear in the stem or branch of a tree cut transversely, consist of different zones of fibres, each the produce of one year's growth, and separated by a coat of cellular tissue, without which they could not be well distinguished. Besides all these, there is the cuticle, which extends over every part of the plant, and covers the bark with three distinct coats.
The root and the stem finally demand notice. The root is designed, not only to support the plant by fixing it in the soil, but also to fulfil the functions of a channel for the conveyance of nourishment; it is therefore furnished with pores, or spongioles, as they are called, from their resemblance to a sponge, to suck up whatever comes within its reach. It is found in a variety of forms, and hence its adaptation to a great diversity of soils and circumstances. We have heard of a willow-tree being dug up, and its head planted where its roots were, and these suffered to spread out in the air like naked branches. In course of time the roots became branches, and the branches roots, or rather roots rose from the branches beneath the ground, and the branches shot from the roots above. Some roots last one year, others two, and others, like the shrubs and trees which they produce, have an indefinite period of existence; but they all consist of a collection of fibres, composed of vascular and cellular tissues, without tracheæ, or breathing-vessels. The stem is the grand distributor of the nourishment taken by the roots to the various parts of the plant. The seat of its vitality is in the point or spot called the neck, which separates the stem from the root. If the root of a young plant be cut off, it will shoot afresh; if the stem be taken away it will be renewed.
Vegetables.—We here take the word "vegetable" in its usual acceptation, and not in its literal meaning. We will now more specially consider those vegetable foods that are eaten with, and to some extent supply the deficiences of, meat.
For convenience sake, these vegetables may be divided into four classes: 1, roots and tubers; 2, pulses; 3, leaves and salads; 4, fungi.
It is a rough classification, and some vegetables will not fall of themselves into either class, but it will serve for our present purpose.
Roots and Tubers.—Of roots and tubers the principal one is the potato. Brought from South America by Sir Francis Drake and Sir Walter Raleigh, it was a long time creeping into public favour, and even in the eighteenth century we find Bradley, a considerable authority on gardens, writing: "They are of less note than horseradish, radish, scorsonera, beets, skirret, but as they are not without admirers I will not pass them by in silence." In Mortimer's Garden Kalendar, written in the 18th century age, he tells how, when he had to feed the poor of Munich, the prejudice against potatoes was so strong that he was obliged to prepare them in secret, and to let none of the people know what thickened the soup they liked so well, but when once accustomed to the new food they preferred it to any other soup.