ROOTS. 417 



large root-cap is evident. The banyan tree of India is a classic 

 example of prop roots for supporting the wide-reaching branches. 

 The mangrove in our own subtropical forests of Florida is a 

 nearer example. 



798. Buttresses are formed at the junction of the root and 

 trunk, and therefore are part root and part stem. Splendid 



Fig. 449. 

 Buttresses of silk-cotton tree, Nassau. 



examples of buttresses are formed on the silk-cotton tree. They 

 are sometimes formed on the elm and other trees in low swampy 

 ground. 



799. Fleshy roots, or root tubers. These are enlargements of 

 the root in the form of tubers, as in the sweet potato, the dahlia, 

 etc. They are storage reservoirs for food. Portions of the roots 

 become thick and fleshy and contain large quantities of sugar, 

 as in the sweet potato, or of inulin (a carbohydrate) in the root- 

 tubers of the dahlia and other composites. 



800. Water roots and roots of water plants. These are roots 

 which are developed in the water, or in the soil. Water-roots 

 are sometimes formed on land plants where the root comes in 



