- santly engaged in disposing into order towards subsequent
organization the raw materials of which the earth is composed: it is their office, by their vital forces or powers, to prepare those substances which, after undergoing a thousand modifications, are gradually converted to nobler purposes in the formation of nervous tissues. In directing our consideration towards the various families of plants, we shall at the same time glance at the multitude of animated beings to which they afford nutriment and protection.
The carpet of flowers and of verdure spread over the naked crust of our planet is unequally woven; it is thicker where the sun rises high in the ever cloudless heavens, and thinner towards the poles, in the less happy climes where returning frosts often destroy the opening buds of spring, or the ripening fruits of autumn. Everywhere, however, man finds some plants to minister to his support and enjoyment. If new lands are formed, the organic forces are ever ready to cover the naked rock with life. Sometimes, as at an early period among the Greek Islands, volcanic forces suddenly elevate above the surface of the boiling waves a rock covered with Scoriæ: sometimes, by a long-continued and more tranquil series of phenomena, the collective labours of united Lithophytes[7] raise their cellular dwellings on the crests of submarine mountains, until, after thousands of years, the structure reaches the level of the ocean, when the creatures which have formed it die, leaving a low flat coral island. How are the seeds of plants brought so immediately to these new shores? by wandering birds, or by the winds and waves of
