Page images
PDF
EPUB

plum, cherry, or peach is a drupe. Fruits of this kind, popularly called stone-fruits, have one seed, or sometimes two seeds, surrounded by a hard shell, and around this is a fleshy covering. A berry is a fruit having the seeds amidst a fleshy or pulpy mass, as in the gooseberry and currant. The grape, the orange, lemon, &c., and the melon, cucumber, &c., afford examples of kinds of fruit closely allied to the true berry. A pod or legume 2 is a dry fruit, opening along two edges, so as to split into two halves, to which the seeds are attached. The name pod is also often given to the silique,3 which differs from the legume in having a central piece, from which the valves part when the fruit is ripe, leaving the seeds attached to it, as may be seen in the kale, the turnip, the wall-flower, and all the large order of plants to which these belong. A capsule is a dry fruit, which assumes a very great variety of forms in different plants, and sometimes opens along its whole length by valves, sometimes along part of its length from the top, so that, when open, it is toothed; sometimes by pores, as in the case of the poppy already noticed; and sometimes by throwing off a lid. A nut is a dry one-seeded fruit, with a hard shell which does not open.

5

Seed.—A seed usually consists of a nucleus or kernel, protected by integuments. The nucleus is often entirely formed of the embryo destined to become a new plant; and in this case, the whole store of matter necessary for the nourishment of the young plant in the commencement of its growth is contained in the embryo itself; but in many seeds there is a separate store of matter for this purpose, called the albumen, which also forms part of the nucleus. The presence or absence of the albumen is a distinguishing character of many kinds of plants. The albumen is sometimes so large that the embryo forms only a small part of the seed; sometimes it is horny and hard, as in the vegetable ivory, a species of palm; sometimes it is farinaceous, as in wheat and other corn-plants; sometimes it is rich in oil, as in the poppy. The structure of the embryo itself does not depend upon the presence or absence of albumen. When we take off the integument of a pea or of a bean, seeds that have no albumen, the embryo is at once fully exposed to view, and we find it to consist of two lobes, united together at one point, from which the radicle and the plumule are to spring, the same point that the seed itself grew from, and by which it was attached to the parent plant. These lobes are called seed-leaves or cotyledons (a, a, fig. 72, page 108), and in some plants,

6

1 From Greek drupetēs, quite ripe, from drys, a tree, and piptō, to fall.

2 Latin legumen, from lego, to gather, so called because the seeds are gathered or attached to only one suture or seam.

3 Latin siliqua, a pod.

4 Latin capsula, a little case, diminutive of capsa, a case.

5 A substance like the white of an egg, from Latin albus, white.

Greek, 'a cup-shaped leaf,' from kotyle, a cup.

as the scarlet runner, they come above ground when the young plant begins to grow; in others, as the bean and pea, they remain underground. Cotyledons exhibit a great variety of forms, and are sometimes wrinkled, curved, folded, or twisted. Those of the potato are spiral. Cotyledons are sometimes split into parts, as in firs, so that a seed appears to have many cotyledons instead of two. Plants of which the seeds have two cotyledons are called Dicotyledonous, from the Greek dis, twice. Those of which the seeds have only one cotyledon are called Monocotyledonous, from the Greek monos, one. These terms designate two great classes of plants, which include all the higher kinds of plants; but the lower kinds have an embryo entirely cellular, which is called a spore,1 and gives forth a new root or stem from any part of its surface, according to the circumstances in which it is placed, and not necessarily from a particular point, as is the case in a monocotyledonous or dicotyledonous seed. Such plants are designated Acotyledonous, from the Greek privative a. There is a remarkable correspondence between the structure of the seed and the structure of the stem, so that exogenous plants are dicotyledonous, endogenous plants are monocotyledonous, and acrogenous plants are acotyledonous, and into these three great classes all plants are divided.

Classification of Plants.

About 120,000 species of plants are known, some of them so minute, that they are mere objects of microscopic examination, while others are of vast magnitude. The great object of botanists in their systems of classification is to exhibit the scheme of nature itself; and this is in a great measure accomplished by the division of plants into the three great classes just mentioned. Plants which have much agreement in structure and characters, are grouped together as forming one order, and those in which the resemblance is still closer as forming one genus.

Acrogenous Plants. Of the lowest class of plants, known as Acrogenous, Acotyledonous, or Cryptogamous, which have no flower, the lowest of all are found in the order Alga [Latin, 'sea-weeds or water-weeds']. These abound both in the sea and in fresh water in all parts of the world. Some sea-weeds attain a great size, exceeding in length the tallest forest trees. They have no root, but are merely attached by their base to rocks, imbibing all their nourishment from the water in which they float. Some of the Alga are used for food, as dulse and carrageen or Irish moss. Some of the larger sea-weeds are valuable as yielding kelp, which is obtained by burning them. Kelp, the ashes of sea-weed, contains a large

1 From Greek sporos, seed.

2 So called from their fructification being concealed, from Greek kryptos, concealed, and gamos, marriage.

quantity of soda, and was formerly much used in the manufacture of

glass.

Fungi are another order of the lowest kind of plants. Of this the mushroom is an example. All the Fungi are short-lived, they grow very rapidly, and soon decay. They do not live in water, but generally in moist situations. Many of them are very small, as the different kinds of mould which grow upon decaying animal or vegetable substances. Many of the larger fungi are pleasant and wholesome articles of food, as the common mushroom, the truffle, and the morel. Some of them, however, are very poisonous, and fatal accidents not unfrequently happen from the mistaking of one kind for another.

Another large order is that of Lichens, 'plants that lick up moisture' [Greek leichen, from leichō, to lick]. Some of them form mere crusts upon the stone or bark on which they grow; some are expanded in a leaflike manner; others form filaments and tufts. Lichens growing on rocks may be said to begin the process of forming a soil for other plants. Iceland moss is an example of a lichen used for food. Another kind, popularly known as reindeer moss, affords the chief winter-food of the reindeer in Lapland and other arctic countries.

Ascending in the scale of plant-life to the true acrogenous plants which have stems, roots, and leaves, the first order which demands special notice is that of Mosses, which chiefly abound in cold and moist regions. They are all small plants, but vast multitudes often grow together, covering the ground with a green carpet.

Another great order of acrogenous plants is that of Ferns. The largest ferns, those which become trees, are found only within or near the tropical regions. Few ferns are of much use to man, but their great beauty has led to their very general cultivation, not only in gardens and greenhouses, but in rooms of houses.

Endogenous Plants.-The two most important orders of Endogenous or Monocotyledonous plants are Palms and Grasses. Palms are only found in warm countries, and mostly within the tropics. The palm frequently mentioned in the Bible is the date-palm, which extends into more northern regions than almost any other species. Palms, in general, have tall stems, often shooting above the other trees of a tropical forest, and waving their great leaves in the air. Some of them, however, have very short stems, and some have very long slender stems, which clamber over trees, and depend upon them for support. Such are the rattans of the East Indies, the stems of some of which far exceed in length the most stately trees of the forest. Rattans are much used for making cane-bottomed chairs and for other kinds of wicker-work. The stems of some palms are used in housebuilding, and for other purposes; the great leaves are used for thatching,

1 Plural of Latin fungus, a mushroom.

and often in Eastern countries as umbrellas; the fibres of various parts are used for cordage and clothing; the sap of some species is used as a beverage, and when fermented, resembles a kind of beer or wine -the toddy of India, from which, by distillation, a kind of spirit called arrack is obtained; the soft internal part of the stem of some species yields sago, and a few species are valuable for their fruit. The most important of these are the date-palm and the cocoa-nut palm. The datepalm supplies the inhabitants of Egypt and many other countries with a great part of their food. The cocoa-nut palm is found on the sea-coast of all tropical countries. The nut is valuable as an article of food and for the oil which it yields; and from the husk a kind of cordage is made, called coir; it is also much used for the manufacture of matting.

Grasses clothe a great part of the surface of the earth. To this order belong all the corn-plants, of which the most important are wheat, barley, oats, rye, rice, maize, and millet. Grasses are in general herbaceous plants with hollow jointed stems; but some tropical species, as bamboos, become shrubs or trees. Grasses afford the greater part of the food of oxen, sheep, and other herbivorous animals. The seeds of the corn-plants or cereal1 grasses also supply a principal part of human food. The stems of bamboos are used for various purposes, as timber for the construction of houses, as pipes for conveying water, &c.

Only a few of the other orders of endogenous plants can be mentioned here. The order Liliacea, as its name implies, contains lilies and many other plants remarkable for the beauty of their flowers. To this order belong the medicinal plants called aloes and squills, also the flax-lily of New Zealand, from the leaves of which is obtained the valuable fibre called New Zealand flax.-The order Amaryllidaceæ, from Latin amaryllis, the snowdrop, contains a great number of species having very beautiful flowers, among which are the narcissus, jonquil, and snowdrop. Some useful plants belong to this order, as the onion and leek, and the American aloe, the leaves of which yield a fibre useful for cordage, and the juice of the flower-stem a beverage much used in Mexico, called pulque. The order Iridacea, of which the iris and crocus are examples, is chiefly notable for the beauty of its flowers. An important order of plants, all natives of warm parts of the world, bears the name of Musacea, from Latin musa, the plantain-tree. The plants of this order are among the largest of herbaceous plants, and false stems formed by the stalks of their great leaves give them the appearance of trees. The banana and plantain belong to this order. The plantain is used in many tropical countries as a substitute for bread; and of all the plants which supply human food, it is by far the most productive. The leaves of some of the Musacea yield a useful fibre, and that of one species, a native

1 So called from Ceres, the Grecian and Roman goddess of corn.

of the Philippine Islands, has become a considerable article of commerce, under the name of Manilla hemp.-Orchids (Orchidacea) are a large order of endogenous plants, generally remarkable for the beauty as well as the curious structure of their flowers.

Exogenous Plants.—We now come to Exogenous plants, but of these the orders are so numerous that many which contain valuable species must be left unnoticed. A very important order, Conifera [Latin, 'cone-bearers'], contains pines, firs, larches, cedars, araucarias, junipers, &c. Among the Conifera are the tallest trees in the world, such as the great pines of California (Wellingtonia gigantea),1 which attain a height of 300 feet or more, their stems rising erect almost to the very summit, and without a branch for almost half their height from the ground. Many of the Conifera are very valuable for their timber, which is remarkably resinous. From trees of this order we obtain also turpentine, tar, and pitch.

The Amentaceæ, from Latin amentum, a catkin, are so called from having their flowers in catkins, as willows, poplars, birch, alder, hazels, oaks, beeches, chestnuts, walnuts, &c. It will be seen, from the examples named, that among the Amentaceae are many noble and beautiful trees, and some which are valuable for their fruits. They abound chiefly in the temperate parts of the world. Both the Conifera and Amentacea are destitute of corolla. The order Urticacea, from Latin urtica, a nettle, contains a great number of species, of which the nettle is an example. Many of the species have stinging hairs; and some Indian nettles sting with a severity far beyond that of the nettles of Britain. Yet the common large nettle of Britain, when gathered young and boiled, is perfectly wholesome, and nettle-broth was at one time in common use in Scotland. Hemp, which yields one of the most valuable of fibres, is nearly allied to the nettles, as is also the hop, of which the flowers are used for flavouring beer.

Closely allied to the Urticaceae is the order Moracea, from Latin morum, the mulberry, to which the fig and the mulberry belong. The species are generally trees, and chiefly abound in warm countries, in which many species of fig are found, some of them rapidly covering ruined buildings with their branches and foliage. The banyan, already noticed, is a species of fig. The fruit of the common fig is very superior to that of any other of its genus. The sycamore, sometimes mentioned in the Bible, is another species of fig, the fruit of which is a common article of food in Egypt and Syria. Some species of this order yield abundantly caoutchouc or india-rubber.-To these orders, that called Ulmacea, from Latin ulmus, an elm, is also allied. It consists of trees and shrubs, of which the elms are examples. They have rough leaves, and are valuable as ornamental and timber trees.-The only other order which

1 Named after the late Duke of Wellington.

« EelmineJätka »