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 alsoimportant. 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 10 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, 4c. It may be 3 feet in other species 
of Rhizophora, 
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