I.] BOTANY. 



are amongst the most gigantic of known plants ; the 

 seaweeds of cold seas are also far more bulky than 

 those of tropical regions. 



Besides the plants now growing upon the surface of 

 the earth, the remains of many others that are no 

 longer living anywhere, are found in rocks at various 

 depths beneath it. Of these, those that lived most 

 recently and are hence found in the more newly 

 formed rocks, are like existing plants ; those that 

 lived longer ago are less like existing ones, and are 

 sometimes very different looking indeed. In short, 

 the longer ago the plants lived the less like they were 

 to plants now living : but however different are the 

 plants that lived longest ago, they all seem to have 

 grown much in the same way, to have depended on 

 similar conditions of light, heat, and moisture, and to 

 have followed the same general course of life. 



The Forms of Plants are infinitely varied. 

 As trees, shrubs, herbs, grasses, ferns, &c., they are 

 familiar to all ; but only a small proportion of the 

 Vegetable Kingdom consists of such plants. The 

 bright green covering of banks, tree-trunks, damp 

 walls, and cottage roofs, and the carpeting of forests 

 and wooded valleys, chiefly consist of mosses and moss- 

 like plants, of which several hundred kinds grow in 

 Britain alone. The ocean's surface sometimes swarms 

 with extremely minute plants, to such an extent as to 

 give the water a distinct colour ; and its shores within 

 and beyond the tide level are covered like gardens 

 with sea-plants of many forms and colours. As green 

 and purple slimes, plants also stain damp walls, and 

 the rocks and stones in the bottom of fresh-water 

 streams and along the seashore; as leathery or 

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