USES OF ROOTS. 33 



preparation, will throw out roots and leaf- 

 buds ; the thick, fleshy leaf containing sufficient 

 water to permit of considerable growth 

 taking place. 



7. Some plants grow as parasites upon 

 other kinds of plants ; they thrust their roots 

 into the tissues of their hosts and live by 

 robbing them of sap, thus weakening and 

 often killing the plants on which they grow. 

 Examples of such plants are the bright yellow 

 dodder (Cuscuta) which is often found injuring 

 lime and other trees ; and mistletoe (Loran- 

 thm y ) which is, in some places, common on 

 cacao. The method by which this plant 

 spreads from tree to tree is interesting, 

 (see chapter on fruits.) 



The roots of these parasitic plants have 

 no root-caps and no root-hairs, these structures 

 being unnecessary unjjer the peculiar con- 

 ditions in which these roots grow. Parasitic 

 plants often constitute troublesome pests in 

 the cultivation of cacao, limes, oranges and 

 other fruit trees. 



