height of 7800 feet; and the herbaceous willow creeps 200 or 300 feet higher, accompanied by a few saxifrages, gentians, and grasses; while lichens and mosses struggle up to the imperishable barrier of eternal snow." OTHER INFLUENCES.-Though the conditions of temperature, depending on latitude and altitude, are the most general in their influences, some others, as light, moisture, and soil, are important. A slope towards the midday sun will display not only more profuse vegetation, but a greater number of species than the darker side of the same mountain; and the south side of a tree will exhibit more vigorous growth than the northern. A clayey moorland shows no such rich, green grass as a limestone district; nor do the flowers of a meadow blossom on thirsty sands. Some trees thrive best when exposed to the seabreeze, as the mangrove and cocoa-palm; others are stunted and destroyed by it. In tropical countries, the hot, dry season is the torpid one for vegetation, as the cold winter is with us. Some rules of influence cannot be traced. No one can tell why it is that certain forms of vegetable life prevail in certain areas, and give it an aspect which belongs to no other. So do the tea-plant and camellia in Eastern Asia; the dull-looking gum-trees and leafless acacias in Australia; the magnolia in America; a cactus here, a mimosa there; heaths, excluding everything else, in one place, grasses in another, and thistles somewhere else. HUMAN INFLUENCE.-Though every plant seems to have some locality where it is most at home, and has vigour to drive out intruders, yet the human will appears, under favourable circumstances, able to overcome these tendencies. The cocoa-nut palm transferred to India from the western world, has monopolised the ground of many native species in Ceylon, which now exports millions of nuts every year. The potato, which came from America some centuries ago, occupies a large portion of the soil in our own islands. Wheat, which Europeans introduced to America, now covers thousands of acres where native forests once had sole possession. Thus the actual vegetation in long-settled countries is extremely complicated, and comparatively few of the plants most extensively cultivated are indigenous. MARINE DISTRIBUTION.-There is in the waters, as well as on land, a certain distribution, both horizontal and vertical; but as the extremes of heat and cold are not so great, the areas of marine vegetation are less distinctly marked. The recognised horizontal zones are— 1. The Northern Ocean, from the pole to the 60th parallel. 2. The North Atlantic, between the 60th and 40th, the head-quarters of the sea-wrack proper. 3. The Mediterranean, from the 40th to the 23d. 4. The Tropical Atlantic, characterized by the weed sargassum, which causes part of it to be called the grassy sea. 5. The Antarctic, south of the 50th parallel, containing peculiar species of enormous dimensions, form ing extensive submarine forests of tangled weed off the coasts of Patagonia. 6. The Australian and New Zealand, where the species are quite distinct, some of them resembling the British. 7. The Indian Ocean and Red Sea, abounding with a weed resembling chopped hay. 8. The Japan and China seas, exhibiting other peculiarities. The vertical distribution in the ocean is termed bathymetrical (bathys, deep), and is regulated by light, depth, and the nature of the sea bottom. The littoral zone is that which lies between high and low water-mark, showing chiefly dulse, carrageen bladder, wrack, &c. The laminarian (lamina, a plate or layer) extends from low water-mark to a depth of sixty feet, and characterized by the broad tangle and larger is algæ. SUMMARY.-Vegetation naturally varies, according to the elevation of the land above the sea-level. The lowest, and therefore warmest, regions produce bananas and palms; and as we go higher, we find districts successively marked by the presence of tree-ferns, Peruvian bark trees, ivies, heaths, grasses, lichens. In the temperate zone a similar gradation is noticed. The Alps, for example, exhibit vines at its feet, oaks and chestnuts to a height of 4000 feet, birch trees to 4800, and pines to 6000. Beyond this is the region of rhododendrons, then of scanty pastures, which disappear on the verge of eternal snow. Latitude and altitude are, however, modified in their results by the presence of abundance of daylight and of moisture, and by the character of the prevailing rocks. Man, too, often transfers plants to other than their native regions. The ocean has its vertical and horizontal sections of vegetation, though less distinctly marked. The former depend partly on the varying degrees of light, and partly on the nature of the sea bottom in different places. QUESTIONS. Explain what is meant by vertical and horizontal districts of vegetation. What gradations does Humboldt notice on the South American heights? Name the plants and trees found on the several levels of the Alps. To what height does the vine, oak, and pine extend? What plants are found nearest the snow? What minor influences affect the vegetation of any district? Name any plants which have been transferred from one country to another. Name the horizontal zones of the sea. What is the sargassum, and where found? TREES. Attractive is the woodland scene, Now green, now tawny, and, ere autumn yet Have changed the woods, in scarlet honours bright. Century, plur. Lat., centuria; from centum, A hundred years. a hundred. The carpenter is one of the most important of mechanics, as without him we could neither have houses nor furniture. In the picture he is represented as using the plane, a tool that smoothes the surface of the wood. The principal tools used by |