SECT. I. SOILS. 423 



wash the coasts of Great Britain, and are generally 

 attached to stones and rocks near the shore. Some 

 of them are always immersed ; and others which 

 are situated above low water mark are immersed 

 and exposed to the action of the atmosphere alter- 

 nately. But none of them can be made to ve- 

 getate except in the waters of the sea. 



Another subdivision of aquatics is that of river River 

 plants, such as Chara, Potamogeton, and Nym- p a 

 phtea, which occupy the bed of fresh water rivers, 

 and vegetate in the midst of the running stream ; 

 being for the most part wholly immersed, as well 

 as found only in such situations. 



A third subdivision of aquatics is that of paludal Marsh 

 or fen plants, being such as are peculiar to lakes, p ants 

 marshes, and stagnant or nearly stagnant waters, 

 but of which the bottom is often tolerably clear. 

 In such situations you find the Isoetis lacustris, 

 Flowering Rush, Water Ranunculus, Water Lily, 

 and a variety of others which uniformly affect such 

 situations, some of them being wholly immersed 

 and others immersed only in part. 



SUBSECTION II. 



'Earthy Soils. Earthy soils are such as emerge 

 above the water and constitute the surface of the 

 habitable, globe that is every where covered with 

 vegetable productions. Plants affecting such soils, 



