TANBARKS 123 
Many mangrove swamps in the Philippines have been so thor- 
oughly depleted of the larger-sized and more valuable trees that 
even though they cover extensive areas they would not be cap- 
able of supporting a cutch factory. However, there are areas 
in Mindanao, Mindoro, and Palawan which, although they may 
not be as large as some in Borneo, still offer promising sites 
for cutch factories. In Sibuguey Bay, Mindanao, there is a 
well-developed swamp covering an area of 25,000 hectares. Con- 
cerning this area Williams + says: 
I have found that this area will yield about 20 metric tons per hectare of 
fresh bark of mature trees of selected species averaging about 28 to 30 per 
cent of tannin on the dry weight. Only four species are included in this 
estimate, all others being negligible from a commercial standpoint. The 
natural resources are sufficient for a profitable industry, the swamps being 
fully as valuable, hectare for hectare, as many now being worked in the 
East Indies. 
A survey of the data shows that only four species can be depended upon 
to furnish a supply of bark. They are Rhizophora mucronata, R. con- 
jugata [candelaria], Bruguiera gymnorrhiza [conjugata], and B. eriopetala 
[sexangula], the two former commonly known as “bacauan” [bakauan- 
lalaki and bakauan-babaye respectively], the two latter as ‘“pototan” or 
“pitutan.” Tangal, which is the “tengah” bark of Borneo upon which the 
manufacturers there depend to a considerable extent, is scarce on Sibuguey 
Bay. Both Xylocarpus granatum [moluccensis] and X. obovatus [grana- 
tum] yield too small quantities of bark per tree to be remunerative. Bru- 
guiera parviflora has a very low tannin content, as has Sonneratia pagatpat 
[caseolaris]. 
However, a use may be found for the last mentioned for blending with 
the more valuable barks, since it produces a leather of good, brown color, 
very different from any tanned by barks of the Rhizophoraceae. 
In calculating the yield of bark in the area examined, only bacauan and 
pototan tree 20 centimeters or more in diameter have been counted. For 
this purpose seven rectangular areas of about one-fourth hectare each were 
selected as representative after a fairly thorough exploration of the sur- 
rounding swamp. These areas are distributed at approximately regular 
intervals between the mouths of the Vitali and Buluan Rivers. The yield 
of bark per tree was determined by felling three representative trees each 
of bacauan and pototan and stripping and weighing the bark. Bacauan 
averaged 140 kilograms per tree, pototan 190 kilograms. On this basis the 
area will yield 20.6 metric tons of bacauan bark per hectare, and 5.8 tons 
of pototan. We may safely state the yield at 20 tons per hectare of bark... 
In Mindoro there is a tract of 10,000 hectares and in Palawan 
a fairly compact area of good swamp. The swamps in the 
other islands of the Archipelago are so scattered as to make the 
success of a cutch factory doubtful. 

+ Williams, R. R., The economic possibilities of the mangrove swamps 
of the Philippines, Philippine Journal of Science, Sec. A, Vol. 6 (1911), 
page 47, 
