20 



ROOTS 



water which drips from branches and trunks above them, so 

 that these plants require no soil and grow suspended in mid air 

 from trees which serve them merely as supports ; many such 

 air plants are grown in greenhouses. In such plants as the ivy 

 (Fig. 14) the aerial roots, which are also adventitious, hold the 

 plant to the waU or other surface up which it climbs. 



In the Indian corn (Fig. 15) roots are sent out from nodes at 

 some distance above the ground and descend until they enter 



; FIG. 14. Aerial, adventitious roots of the ivy 



the ground. They serve to anchor the cornstalk so that it may 

 resist the wind, and to supply additional water to the plant. They 

 often produce no rootlets until they reach the ground. 



28. Water roots. Many plants, such as the willow, readily 

 adapt their roots to live either in earth or in water, and some, 

 like the little floating duckweed, regularly produce roots which 

 are adapted to live in water only. These water roots often show 

 large and distinct sheaths on the ends of the roots, as, for 

 instance, in the so-called water hyacinth (Eichliomia). 



