343 
refers to the whole amount of extract in the bark and not to 
the tannin alone. I think it most likely that our different man- 
groves will ordinarily be found to yield percentages of tannin 
running between 15 and 35°/, by weight of the dry bark. . 
The treatment of the bark to secure the extract seems to 
be a very simple process. The parenchyma tissue of the bark 
is filled with tannin which it given up very readily. 
Mangrove-cutch is used for the following purposes: Dyeing 
and tanning fishing-nets and -lines, tanning sails, tanning lea- 
ther, coloring tea, dyeing blue and black Chinese cloth (mixture 
of Tengah and indigo). 
Tengah (Ceriops spp.) bark is generally considered the best 
of the mangroves; but, it has the disadvantage of high color. 
Red putut (Bruguiera gymnorrhiza) furnishes the best bark of 
any of the Réizophora or Bruguiera species. 
The method of extraction of the extract from the bark seems 
to be comparatively simple and the supply of mangrove-bark 
is very great. It seems safe to say that the island of Borneo 
could supply a sufficient amount of tanbark for the whole 
world for a number of years; and, if the swamps were con- 
servatively managed, could do so indefinitely. 
Timber and firewood. 
The larger trunks and some of the smaller ones as well, 
are often used for piling. It is said that they will resist the 
teredo for a number of years. Whenever it is necessary to 
drive piling before putting in foundations, the mangroves are 
in demand. For this purpose it seems that they will last inde- 
finitely. It is doubtful if any other wood is so well suited for 
this class of work. 
All of the mangroves (with the exception of Kandela) have 
very hard and very heayy wood, often heavier than water 
when dry. All of them furnish excellent firewood; and, in sec- 
tions where the mangrove-swamps are not extensive, or are 
close to thickly populated neighborhoods, they are likely to 
be cut out for firewood. When the swamp is left to itself after 
