Imágenes de páginas
PDF
EPUB

The SAP and PULP of plants, by which they are nourished, as animals are sustained by means of blood, are produced by, and undergo very different changes from those of blood. There being no stomach in plants to digest food, the soil seems to act the part of a stomach, and the tips of the roots which take up the sap, are so admirably constructed, that they only take up the sort of moisture adapted to constitute sap, namely rain water mingled with manure, or other nutritive materials in the soil.

As there is no stomach in plants to digest the sap, no more is there any heart to circulate the same throughout the plant, and it is not well understood, éven by the best informied botanists, in what manner this circulation is effected, unless it be that the sap rises through the tissue of the plant, particularly through the inner lays of the bark, and between the annual rings of the wood, in some similar way to that in which water spreads through blotting paper, or rises up through a piece of lump sugar. .

When the air is warm, and the sun shining on the leaf, a large portion of the sap is 'exhaled, and the sap which remains is consequently rendered thicker by this loss of its water ; but so far from any of the darker-coloured substance, or 'carbonaceous matter being carried off, as it is from the blood in animal lungs, a portion of the carbon in the air is imparted to the sap ; while oxygen, contrary to what takes place in the lungs, is given off. The sap is both rendered of a thicker. consistency and much more carbonaceous quality than before, and according to some eminent authorities, is not exactly black as it appears, but of a dark blue colour.

The gap, after it has undergone these changes, passes to the under side of the leaf, and is returned through the foot-stalk to nourish the branches, the stem, the root, and other parts of the plant, in the same way as blood is passed back by arteries from the lungs to the heart, to be sent to all parts of the animal body.

1. Vide Root.

AUSTRALIA AND POLYNESIA.

Their Discovery and present condition. * AUSTRALASIA 'comprises New Holland, New Guinea, Van Diemen's Land, and the other islands in the vicinity.

New Holland is an 'immense island containing three millions of square miles, and is abont as large as Europe. This great island was discovered by the Dutch, in 1610, but the whole of it is now claimed as a territory of Great Britain. Captain James Cook, the celebrated navigator, took possession of it in 1770.

It is now divided into two colonies. The eastern is called New South Wales, and the western the Swan river colony. New South Wales is the oldest, and began to be settled in 1778. It was then called Botany Bay. South Australia is a new colony which is rapidly improving. New Zealand, New Guinea, Sumatra, and Java, are all important islands included under the term Australia. New Zealand is likely to become, before long, an important British colony.

POLYNESIA is the name given to many groups of small islands, which are scattered over a large extent of the Pacific Ocean. None of them are inhabited by civilized people.

The Sandwich islands are among the most important. They consist of ten islands, of which Owhyhee, or Hawaii, is the largest. These islands were discovered by Captain James Cook, in 1778.

The natives at first behaved in a very friendly manner to Captain Cook. But, after some time, a part of them stole one of the boats belonging to his vessel. The captain went on shore, intending to take the king of Hawaii prisoner, and keep him till the boat should be returned. But when he had landed, the natives mustered in great numbers. Captain Cook found it necessary to retreat towards his own men, who were waiting for him in a boat near the shore. The natives followed him, shouting, throwing stones, and brandishing their weapons. One of them beat him down with a club, and then stabbed him with a dagger. His men fired their muskets at the natives, but could not rescue him.

1. Vide Root.

The Sandwich islands soon after became the resort of whale-ships, and of all other vessels that voyaged in that part of the Pacific Ocean.

The Society islands likewise belong to Polynesia. They are situate about a thousand miles south of the equator, which is nearly the same distance that the Sandwich islands are north of it. The largest of the Society islands is called Tahiti or Otaheite.

The inhabitants of these numerous, large, and widely scattered islands are among the most savage of the human zace. Many of them are cannibals. By the blessing of God upon the efforts of English and American missionaries, the gospel of Jesus Christ has now been planted in many of these islands, and through the agency of native teachers it is rapidly diffusing.

In many of the islands scarcely any labour is required to obtain sufficient food, the bread-fruit, plantain, cocoa nuts, fish, and fresh water being abundant GEOGRAPHICAL.-What lines of latitude and longitude bound New Holland ? What is the difference in time between London and Hobart Town in Van Diemen's is 14} sd

* Land ? Which is the shorter route from England to Hobart Town, by the Cape of Good

Hope or by Cape Horn ?
CARONOLOGICAL.-Sumatra discovered by the Portuguese ...... 1008
; The Moluccas, Sunda Islands, Maldives, Borneo, and Jaya, 1513

New Holland first visited by the Portuguese .............. 1525
Japan ........... ditto .......

1542 Otabeite discovered by Wallis ........

1767 Sandwich Islands and others by Captain Cook ............. 1778

VEGETABLE PHYSIOLOGY.

11) Seed and Organs of Fructification. Seep.-Looking at the different forms and dimensions of seeds, the extraordinary manifestation of Divine wisdom and skill in their structure, is exceedingly striking and interesting. Take, for example, the seed of a sweet-pea, which is not much larger than the head of a small pin, yet within these narrow dimensions are compactly folded up a large, branchy, flowering plant, which may attain the height of seven or eight feet, and exhibit hundreds of fragrant blossoms during several of the summer months."

The cause of the general smallness of seeds, appears to be the greater ease with which they can be diffused and preserver. Were the seeds of the oak to be as large, when compared with those of the scarlet-runner or the longpod bean, as the oak tree is larger than the bean plants, it would present innumerable difficulties to the extensive diffusion of the species. In order to be successfully sown, the seeds must be covered with earth, decayed leaves, or the like; but if the acorns were the size of a large cabbage, when they fell from the tree it would rarely happen that they could be so covered, except by art.

The concentration of the vital principle of vegetation within a small space, has also the effect of enabling seeds to resist the influence of agents which might otherwise prove destructive, such as extraordinary degrees of heat or cold.

Recent experiments prove that some seeds may be subjected, for a short time, to the heat of boiling water, 212 deg. of Fahrenheit's thermometer, without injuring their vegetating properties; and it requires the most intense frost to destroy the greater number of seeds, while some sorts might resist the greatest cold that could be produced.

Flowers. The calyx, or flower-cup, is the external covering which protects the bud before it expands; it consists of several parts, resembling small leaves both in form and colour.

Above and within the calyx lies the 'corolla, which is the coloured part of the flower; it is composed of several

petals. When the petals burst from the calyx, and expand in all their beauty, they still serve to protect the central part of the flower. They are at first curved inwards, forming a 'concarity around the delicate organs which occupy the centre. This not only shelters them from external injury, but reflects the sun's rays upon them, like a concave mirror, thus rearing them, as it were, in a hot-house.

At the base of the petals is generally situated an organ called the nectary; this is the store whence the bee derives honey.

The most important parts of the flower are those organs which occupy the centre. It is here that the seed, which is to propagate the plant, is lodged in a vessel, called the ovary, or seed-vessel. From its summit rises a little thread-like stalk, calied the style, which, at its extremity, supports a small spongy substance, denominated the stigma. These three parts form a whole, which bears the name of pistil.

Immediately surrounding the pistil or pistils are situated the stamens, each of which consists of a slender filament supporting a little bag or case, called an anther, filled with pollen, which is a sort of dust or powder. The anthers, when ripe, burst; and being more elevated than the stigma, shed their pollen upon it; without which no seed can be perfected.

1. Vide Root.

« AnteriorContinuar »