124 



PHYSICAL GEOGEAPIIY. 



[Part I. 



iiig on the surface of tlie water. It is borne aloft by masses 

 of a spongy cellular substance, which occur at intervals 

 along its stem and branches, but the roots never touch the 

 bottom, absorbing nourishment whilst floating at liberty, 

 and only found in contact with the ground after the sub- 

 sidence of water in the tanks. ^ 



' A species of Utricularia, with 

 yellow flowers (U. stellaris), is a 

 common water-plant in the still lakes 

 near the fort of Colombo, where an 

 opportimity is aftbrded of observing 

 the extraordinary provision of nature 

 for its reproduction. There are small 

 appendages attached to the roots, 

 which become distended with air, and 

 thus cany the plant aloft to the sui'- 



face, diu'ing the cool season. Here 

 it floats till the operation of flowering- 

 is over, when the vesicles biu'st, and 

 by its OAvn weight it retm-ns to the 

 bottom of the lake to ripen its seeds 

 and deposit them in the soil ; after 

 which the air vessels again fill, and 

 again it re-ascends to undergo the 

 same process of fecimdation. 



