THE AMERICAN BOTANIST 45 



70 — 80 feet, with a fine tall straight trunk, 3 — 4 feet in 

 diameter and clear of branches for more than half its length. 

 These trees, of course, yield the best timber. Normally, how- 

 ever, the tree is squat and broad and as it grows it throws out 

 great numbers of aerial roots, which brace it wtII on all sides, 

 like those of the Pandanus or banyan, so that the waves and 

 tides cannot dislodge it. The roots branch profusely in the 

 air and spread out laterally, forming a dense network. They 

 are of special importance in supporting the numerous branches 

 as in most cases the basal part of the primary trunk has an 

 early death. The roots themselves are very stem-like in in- 

 ternal structure. The aerial roots or pneumatophores com- 

 prise an interesting feature of this tree. These are erect 

 branches of the roots, which project above the mud and are 

 provided with stomata and lenticels, into which air passes 

 freely and is then carried by means of passages in the soft 

 spongy tissues to the underground roots. Like certain other 

 aquatic plants, the mangrove develops intercellular or internal 

 hairs in its air-passages. These hairs are of ecological sig- 

 nificance in connection with the fluctuations in the air-supply, 

 which varies greatly, of course, with the rise and fall of the 

 tides. 



The bark is at first smooth, reddish brown, becoming 

 .3 5-. 50 inches thick and gray faintly tinged with red. The 

 surface is irregularly fissured into low close ridges, these 

 again are transversely broken into thin appressed scales, giving 

 a very characteristic appearance to the old bark. The bark is 

 red inside. It is rich in tannin and is used for tanning leather 

 and also in dying. The Florida Indians formerly used the 

 copious bast for an excellent cordage. A decoction of the 

 bark is used by the natives of tropical American as a febrifuge. 



The wood is very heavy, weighing 72.40 lbs. per cubic 

 foot of seasoned wood. It is very hard, tough, and durable. 

 It is close-grained and takes a beautiful satiny polish. The 



