PHILIPPINE DIPTEROCARPACEAE. 
243 
Of course, the chopping into the trees to get the flow of oil is very 
injurious to them and causes the destruction of much good timber by 
leaving the tree a prey to fungous attack. In some localities nearly all 
the mature Dipterocarpus trees are tapped. In spite of this loss of 
standing timber, the collection of the oil may be justified from the 
viewpoint of practical forestry, wherever the value of the oil is greater 
than that of the timber destroyed. It would certainly seem, however, 
that the tree which had been tapped should be felled, whenever it has 
ceased to yield oil. I do not know how long a tree will continue to 
yield oil, nor whether it would be desirable to make successive tappings, 
nor whether it would be feasible to extract the oil from the wood by 
distillation. The bark does not seem to be a commercial source of the 
oil, although it does contain an oily or mucilaginous substance in some 
quantity. 
The timber, is grayish-red, coarse-grained, moderately hard and moder- 
ately heavy. It is remarkably uniform in structure for the different 
species, although there is a considerable range in texture and hardness. 
It is much subject to termite attack; but in places where it is protected 
from excessive moisture and from termite attack, it should be quite 
durable. It has a great deal of strength and stiffness and is well suited 
to heavy construction work and framing. It is in fair demand and 
commands a price of 70 to 90 pesos ($35 to $45) per thousand feet B. M. 
on the Manila market. The trees are of good shape and are readily 
logged, but the logs behave badly on the saw. The large amount of 
gummy oil present interferes with sawing, dulling the saws quickly and 
even pulling the teeth out now and then. It is customary to keep a 
stream, of water dripping ou the running saw to lessen this difficulty. 
In spite of this disadvantage in conversion, the handling of this timber 
is a very profitable business. 
All of our species are gregarious in habit. Some species, e. g. I). 
grandiflorus, are often found on steep and exposed dry ridges; others, 
like D. pilosus, are more often found on low flat land. 
The genus contains about 60 species, 11 of them being found in the 
Philippines. Of the Philippine species, 5 are known to be extra-Philip- 
pine in distribution, and it is quite likely that this will be found to be 
true of a greater number of our species, when we know them better. 
Leaf fall and seasonal . growth. — Dipterocarpus gra/ndiflorus, at any 
rate, and probably other species, shows a distinct periodicity in leaf fall. 
It seems that each tree sheds all of its leaves each year and at about the 
same time; but the tree is never leafless. It seems that the tree has the 
new leaves ready formed in the bud and that the old leaves do not fall 
till pushed off by the expansion of the new. Brandis, 1. c. 9 says : “Most 
dipterocarps are evergreen, the old leaves falling soon after the young 
