VEGETATION OF SExl- WEEDS. 29^ 



ment partly by their roots from the soil, and partly from 

 the air by their leaves. There can be no doubt as to their 

 being nourished by their roots, for manure applied to the 

 roots soon tells upon the plants ; and tliey extend far in 

 search of nourishment. Many think, hoNvever, that sea- 

 plants derive all their nourishment from the water, or the 

 air when exposed to it, by means of their general surface, and 

 that the roots are scarcely of any use except to attach them 

 to the rock or other substance on which they grow. In 

 confirmation of this opinion they mention that Sargasstim 

 hacciferimij or Gulf- weed, which floats in such mighty masses 

 in some seas, not only seems to grow in this floating state, 

 but that this floating piece of Sargassum has never been 

 found attached by roots. It may nevertheless yet be found 

 in a young state attached by roots, though it may still be 

 true that it can grow in this floating state. Take a branch 

 of Cladopliora glonierata from a plant adhering by roots to 

 a stone in fresh water, and place the branch in a vase of 

 fresh water, and it will grow and increase considerably. 

 Though a land-plant suspended in the air without getting 

 nourishment by the roots would soon wither, yet you know 

 that some of the Epidendra, air-plants as they are called, 

 are exceptions from this, for if they are hung up in a room 



