Flora Hongkongensis/1/1
INTRODUCTION.
OUTLINES OF BOTANY, WITH SPECIAL REFERENCE TO LOCAL FLORAS.
CHAP. I. DEFINITIONS AND DESCRIPTIVE BOTANY.
1. The principal object of a Flora of a country, is to afford the means of determining (i. e. ascertaining the name of) any plant growing in it, whether for the purpose of ulterior study or of intellectual exercise.
2. With this view, a Flora consists of descriptions of all the wild or native plants contained in the country in question, so drawn up and arranged that the student may identify with the corresponding description any individual specimen which he may gather.
3. These descriptions should be clear, concise, accurate, and characteristic, so as that each one should be readily adapted to the plant it relates to, and to no other one ; they should be as nearly as possible arranged under natural (184) divisions, so as to facilitate the comparison of each plant with those nearest allied to it ; and they should be accompanied by an artificial key or index, by means of which the student may be guided step by step in the observation of such peculiarities or characters in his plant, as may lead him, with the least delay, to the individual description belonging to it.
4. For descriptions to be clear and readily intelligible, they should be expressed as much as possible in ordinary well-established language. But, for the purpose of accuracy, it is necessary not only to give a more precise technical meaning to many terms used more or less vaguely in common conversation, but also to introduce purely technical names for such parts of plants or forms as are of little importance except to the botanist. In the present chapter it is proposed to define such technical or technically limited terms as are made use of in these Floras.
5. At the same time mathematical accuracy must not be expected. The forms and appearances assumed by plants and their parts are infinite. Names cannot be invented for all ; those even that have been proposed are too numerous for ordinary memories. Many are derived from supposed resemblances to well-known forms or objects. These resemblances are differently appreciated by different persons, and the same term is not only differently adopted by two different botanists, but it frequently happens that the same writer is led on different occasions to give somewhat different meanings to the same word. The botanist's endeavours should always be, on the one hand, to make as near an approach to precision as circumstances will allow, and on the other hand to avoid that prolixity of detail and overloading with technical terms which tends rather to confusion than clearness. In this he will be more or less successful. The aptness of a botanical description, Uke the beauty of a work of imagination, will always vary with the style and genius of the author. § 1. The Plant in General.
6. The Plant, in its botanical sense, includes every being which has vegetable life, from the loftiest tree which adorns our landscapes, to the humblest moss which grows on its stem, to the mould or fungus which attacks our provisions, or the green scum that floats on our ponds.
7. Every portion of a plant which has a distinct part or function to perform in the operations or phenomena of vegetable life is called an Organ.
8. What constitutes vegetable life, and what are the functions of each organ, belong to Vegetable Physiology ; the microscopical structure of the tissues composing the organs, to Vegetable Anatomy ; the composition of the substances of which they are formed, to Vegetable Chemistry ; under Descriptive and Systematic Botany we have chiefly to consider the forms of organs, that is, their Morphology, in the proper sense of the term, and their general structure so far as it affects classification and specific resemblances and differences. The terms we shall now define belong chiefly to the latter branch of Botany, as being that which is essential for the investigation of the Flora of a country. We shall add, however, a short chapter on Vegetable Anatomy and Physiology, as a general knowledge of both imparts an additional interest to and facilitates the comparison of the characters and affinities of the plants examined.
9. In the more perfect plants, their organs are comprised in the general terms Root, Stem, Leaves, Flowers, and Fruit. Of these the three first, whose function is to assist in the growth of the plant, are Organs of Vegetation ; the flower and fruit, whose office is the formation of the seed, are the Organs of Reproduction.
10. All these organs exist, in one shape or another, at some period of the life of most, if not all, flowering plants, technically called phænogamous or phanerogamous plants ; which all bear some kind of flower and fruit in the botanical sense of the term. In the lower classes, the ferns, mosses, fungi, moulds or mildews, seaweeds, etc., called by botanists cryptogamous plants, the flowers, the fruit, and not unfrequently one or more of the organs of vegetation, are either wanting, or replaced by organs so different as to be hardly capable of bearing the same name.
11. The observations comprised in the following pages refer exclusively to the flowering or phænogamous plants. The study of the cryptogamous classes has now become so complicated as to form almost a separate science. They are therefore not included in these introductory observations, nor, with the exception of ferns, in the present Flora.
12. Plants are
Monocarpic, if they die after one flowering-season. These include Annuals, which flower in the same year in which they are raised from seed ; and Biennials, which only flower in the year following that in which they are sown.
Caulocarpic, if, after flowering, the whole or part of the plant lives through the winter and produces fresh flowers another season. These include Herbaceous perennials, in which the greater part of the plant dies after flowering, leaving only a small perennial portion called the Stock or Caudex, close to or within the earth ; Undershrubs, suffruticose or suffrutescent plants, in which the flowering branches, forming a considerable portion of the plant, die down after flowering, but leave a more or less prominent perennial and woody base ; Shrubs (frutescent or fruticose plants) , in which the perennial woody part forms the greater part of the plant, but branches near the base, and does not much exceed a man's height ; and Trees (arboreous or arborescent plants) when the height is greater and forms a woody trunk, scarcely brandling from the base. Bushes are low, much branched shrubs.
13. The terms Monocarpic and Caulocarpic are but little used, but the other distinctions enumerated above are universally attended to, although more useful to the gardener than to the botanist, who cannot always assign to them any precise character. Monocarpic plants, which require more than two or three years to produce their flowers, will often, under certain circumstances, become herbaceous perennials, and are generally confounded with them. Truly perennial herbs will often commence flowering the first year, and have then all the appearance of annuals. Many tall shrubs and trees lose annually their flowering branches like undershrubs. And the same botanical species may be an annual or a perennial, a herbaceous perennial or an undershrub, an undershrub or a shrub, a shrub or a tree, according to climate, treatment, or variety.
14. Plants are usually terrestrial, that is, growing on earth, or aquatic, i. e. growing in water; but sometimes they may be found attached by their roots to other plants, in which case they are epiphytes when simply growing upon other plants without penetrating into their tissue, parasites when their roots penetrate into and derive more or less nutriment from the plant to which they are attached.
15. The simplest form of the perfect plant, the annual, consists of—
(1) The Root, or descending axis, which grows downwards from the stem, divides and spreads in the earth or water, and absorbs food for the plant through the extremities of its branches.
(2) The Stem, or ascending axis, which grows upwards from the root, branches and bears first one or more leaves in succession, then one or more flowers, and finally one or more fruits. It contains the tissues or other channels (217) by which the nutriment absorbed by the roots is conveyed in the form, of sap (192) to the leaves or other points of the surface of the plant, to be elaborated or digested (218), and afterwards redistributed over different parts of the plant for its support and growth.
(3) The Leaves, usually flat, green, and horizontal, are variously arranged on the stem and its branches. They elaborate or digest (218) the nutriment brought to them through the stem, absorb carbonic acid gas from the air, exhaling the superfluous oxygen, and returning the assimilated sap to the stem.
(4) The Flowers, usually placed at or towards the extremities of the branches. They are destined to form the future seed. When perfect and complete they consist: 1st, of a pistil in the centre, consisting of one or more carpels, each containing the germ of one or more seeds; 2nd, of one or more stamens outside the pistil, whose action is necessary to fertilize the pistil or enable it to ripen its seed; 3rd, of a perianth or floral envelope, which usually encloses the stamens and pistil when young, and expands and exposes them to view when fully formed. This complete perianth is double; the outer one, called Calyx, is usually more green and leaf-like; the inner one, called the Corolla, more conspicuous, and variously coloured. It is the perianth, and especially the corolla, as the most showy part, that is generally called the flower in popular language.
(5) The Fruit, consisting of the pistil or its lower portion, which persists or remains attached to the plant after the remainder of the flower has withered and fallen off. It enlarges and alters more or less in shape or consistence, becomes a seed-vessel, enclosing the seed until it is ripe, when it either opens to discharge the seed or falls to the ground with the seed. In popular language the term fruit is often limited to such seed-vessels as are or look juicy and eatable. Botanists give that name to all seed-vessels.
16. The herbaceous perennial resembles the annual during the first year of its growth; but it also forms (usually towards the close of the season), on its stock (the portion of the stem and root which does not die), one or more buds, either exposed, and then popularly called eyes, or concealed among leaves. These buds, called leaf-buds, to distinguish them from flower-buds or unopened flowers, are future branches as yet undeveloped; they remain dormant through the winter, and the following spring grow out into new stems bearing leaves and flowers like those of the preceding year, whilst the lower part of the stock emits fresh roots to replace those which had perished at the same time as the stems.
17. Shrubs and trees form similar leaf-buds either at the extremity of their branches, or along the branches of the year. In the latter case these buds are usually axillary, that is, they appear in the axil of each leaf, i. e. in the angle formed by the leaf and the branch. When they appear at any other part of the plant they are called adventitious. If these buds by producing roots (19) become distinct plants before separating from the parent, or if adventitious leaf-buds are produced in the place of flowers or seeds, the plant is said to be viviparous or proliferous.