AMERICAN FOREST TREES 



Trees which have their beginning in the water sometimes end their days 

 high and dry on the land. 



The mangrove is a land builder. The sycamore and willow are 

 land builders on a small scale, along northern water-courses, but man- 

 grove excels them a hundred or a thousand fold where it grows on the 

 low shores of Florida. The seed is prepared for land-building work 

 before it drops from the tree. It sprouts a long, peculiar root it looks 

 like a very slender, big-ended cucumber the large, heavy end down. 

 This attains a length of several inches or a foot. When it drops from 

 the branch, the end sticks in the mud and takes root, grows, and pro- 

 duces a tree. But generally it falls in water, and not on a mud bank. 

 In that case it floats away, the heavy end down, the light end barely 

 appearing on the surface. Winds and currents drive it about until the 

 lower tip finally touches bottom in some shallow place. There it takes 

 root, and unless circumstances are extremely adverse, it holds fast, 

 finally becomes a tree, sends branches down from above to take root at 

 the bottom of the water, and a clump is produced. The tangled mass of 

 stems and roots catches driftwood and mud, resulting finally in a little 

 island, and later the island is joined to the mainland. Thus the land is 

 built. Many large flats in Florida owe their origin to this tree. When 

 land is permanently above water, the mangrove loses, to some extent, its 

 ability to send roots down from the limbs. Nature seldom does some- 

 thing for nothing, and since the mangrove's aerial roots no longer serve 

 a useful purpose in nature's economy, they are dispensed with. Trunks 

 then reach much larger size, and become timber instead of thickets. 

 The accompanying picture shows a mangrove that no longer stands in 

 water, and its habit of growth is changing. 



Thickets of mangrove are useful, not only in building new land, but 

 in protecting that already built. Frequently the force of waves is 

 broken, which otherwise would destroy low shores. Tremendous seas, 

 in time of storms, will roll over thickets of mangrove without uprooting 

 them or breaking the stems. Again nature's fine engineering is apparent. 

 When men build lighthouses which must endure the shocks of waves, 

 they have learned to construct them of open beams and lattice work. 

 The wave passes through without delivering the full impact of the blow 

 to the structure. No solid masonry will stand what a comparatively 

 light open frame will endure without injury, because it allows the waves 

 to pass on. A large wave may strike with a force of 6,000 pounds to the 

 square foot. The mangrove thickets are like the open-framed light- 

 house they let the waves pass through and spend their force gradually 

 beyond, but they hold the shore against washing. 



Admirable and wonderful as is nature's provision for protecting the 



