26 MANGROVE SWAMPS 
found in some swamps. This plant has hollow leaves in which 
ants are found. 
Reproduction is prolific in almost all places where seed trees 
are found, except along the higher inland portions of the swamp. 
Back of the swamps are found numerous characteristic 
strand plants, and representatives of nearly all such plants in 
the region may be found in such situations. Among the com- 
mon trees and shrubs back of the swamps are Glochidion littorale 
Blume, Hibiscus tiliaceus Linn., Thespesia populnea Coryr., and 
Barringtonia racemosa Roxb. The sedge Fimbristylis ferru- 
ginea Vahl practically always occurs in such places, while along 
muddy banks Cyperus malaccensis Lam. is very common. 
The chief commercial value of mangrove-swamp trees is for 
the production of firewood, charcoal, tannin, and dye barks. 
Some of the woods are also used for ship timbers, posts, ties, 
telegraph poles, piling, construction, finish, and furniture. 
The nipa palm is very valuable as a source of thatching and 
alcohol and offers considerable possibilities for the production 
of sugar. For a discussion of the products of mangrove trees 
and the nipa palm, see the sections on these various subjects. 
Mangrove trees serve a useful purpose in preserving water 
courses through the deltas at mouths of rivers. That they 
may be used to advantage to retain soil in engineering projects 
is shown by the following quotation :* 
The latest use of the mangrove in a practical way and one of which 
the writer has personal knowledge is the use of these trees as ballast 
retainers. This has been effectively demonstrated by the Florida East 
Coast Railway which has used the peculiar habit of the mangrove to 
advantage in their great feat of engineering, viz., the Oversea extension. 
At certain places these keys are connected by embankments supporting 
the road bed or where the bed is built high over a low flat key, the 
mangroves have been planted to prevent the erosive action of the sea 
on the ballast. This has been of greatest importance to the railroad and 
has protected the dykes just as the mangroves naturally sown have 
formed and protected young islands. Still more recently the writer has 
been of some small service to a large asphalt company concerning their 
engineering projects in Venezuela in which it is proposed to plant Rhizo- 
phora mangle along the dykes and jetties, etc., as a ballast retainer. This, 
it is hoped, will prove as efficient as the plantings of the Florida East 
Coast Railway have been in aiding the engineer in the tropics. 
Mangrove swamps occur in similar situations in the tropics 

* Bowman, H. H. M., Ecology and physiology of the red mangrove. 
Proceedings of the American Philosophical Society, Vol. LVI (1917) pp. 
589-672. 
