Tropical Forests 



water. Each root, as soon as it approaches the level of 

 high tide, breaks into four or five rootlets exactly like 

 grasping fingers outstretched to lay hold of the mud. 



When the tide returns and fills the whole system of 

 creeks and lagoons, new deposits of mud are continually 

 being laid down, and new banks are formed. If some 

 such root manages to reach one of these banks it soon 

 establishes itself upon it, and the mangrove swamp has 

 gained a piece of new territory. 



But in this process the seedlings of the genus Rhizo- 

 phora are also important. The seed begins to germinate 

 whilst in the fruit and still attached to its parent tree, 

 which is a most unusual proceeding in the vegetable 

 world, for there is no period of rest, as is usual with 

 almost all other plants. After the flower is fertilised 

 the seedling continues to grow for about thirty-three 

 weeks before it finally falls out of the fruit. By this 

 time the rootlet is about 9 to lo inches long.^ ® Then 

 it begins to free itself forcibly from the fruit by a very 

 remarkable swelling which appears at the base of the 

 seed-leaves. 



If the seedling falls into mud it will at once take root 

 and vigorously grow into a new mangrove ; the outer 

 muddy edge of the mangrove swamp may show quan- 

 tities of such young trees trying to establish themselves. 



But if it drops off at high tide, it floats freely in the 

 water. In fresh water it will be upright, but in salt the 

 young seedling generally floats horizontally. Quantities 

 of such mangrove navigators may be found even ten or 

 twenty miles off the shore, and they may be carried by 

 the currents towards perhaps some as yet uncolonised 

 estuary. They can float without any sign of injury for 

 at least four months. 



Perhaps it is in this way that the mangroves on the 



* Rhizophora mangle, see Guppy, Ic, It may be 3 feet in other species 

 of Rhizophora. 



