8 PHYSIOGNOMY OF PLANTS. 



santly engaged in disposing into order towards subsequent 

 organization the raw materials of which the earth is com- 

 posed : 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 considera- 

 tion 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 sup- 

 port 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 Scoriae : some- 

 times, by a long-continued and more tranquil series of phe- 

 nomena, 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 



