ROOTS AS TO ORIGIN 



127 



Some tropical trees have unusual roots which come 

 from the stem. The banyan is a tree from whose lower 

 horizontal branches roots descend. At first they are like 

 swaying ropes, free at one end. When a free end reaches 

 the soil, it begins to burrow like any root. These prop 

 roots may develop in thickness until they seem like second- 



Fig. 40. — A strawberry plant showing the way in which the creeping stems put 

 off secondary roots and establish new plants. — Redrawn from Bergen. 



ary trunks of the parent tree. The largest banyans have 

 hundreds of these secondary trunks. They cover several 

 acres. At a distance one tree may look like a forest in 

 itself. 



The mangrove swamps along tropical shores are named 

 from plants which gradually grow out into the sea. Like 

 the banyan, they have the habit of dropping new roots 

 from their branches. Among the new roots on the sea- 

 ward side drifting material becomes entangled. This helps 

 in the formation of soil about them. Thus, where the 

 water is shallow, the mangroves "march out to sea." 



