Notes on Dipterocarps. 
No. 7. On the fruit and germination of 
Isoptera borneensis. 
Jepy Wes daly eieaacac ty 
Tsoptera borneensis, Scheft., is a tree which yields much of the 
Tangkawang fat produced in Malaya. Borneo, where its extension 
is through the island, is the centre of its distribution: eastwards 
it reaches Mindanao and westwards the Malay Peninsula, Bangka 
and south Sumatra. It is a large, but apparently not a very large 
tree. Its habitat is the margins of rivers of moderate size. Into 
their waters it drops is fruits, and they are distributed by them. 
The following is a figure of the fruit in the position in which 
it floats, the buoyant sepals upwards. 
Fig. 1. A. seed of Isoptera borneensis, in the position in which it 
floats. 1% nat. size. 
Deprived of the corky sepals, the fruits within 60 hours, 
sink however dry at the starting of the experiment. 
In Note no. 4 of this series (Journ. Straits branch Roy. As. 
Soe. no. 81, 1920, p. 75) an account was given of the floating fruit 
of Vatica Wallichu, Dyer (Pachyvnocarpus Wallichiu, Aing) wherein 
the buoyant tissue is the fruit-wall, i.e. the same end is attained 
but by different means. 
It is not possible to regard water-distribution as in any way 
ancestral in the order; but. it appears in Vatica as an ultimate 
modification at the end of a series which has lost the advantage 
of height and thereby lost the wind that does not reach a small 
mee deep in high forest: and it would seem to be connected with 
fruiting before the tree is of any great height in Lsoptera borneensis ; 
for the tree commences to fruit at the early age of six years s (fide 
van Romburgh and Ridley). But though Vatica Wallichw and 
Isoptera borneensis use water as.a means for the distributing of 
their seeds they have little else in common, being wide apart in 
their order. 
The embryo of Isoptera borneensis is very like that of some 
Shoreas, say of S. costata, in being grooved down the sides and in 
-end-view, as figured here; but both es cotyledons reach the apex 
of the fruit- cavity, though the eee so much the larger that it 
possesses anything from 240: to 2 oe of the sivommnffemence 
‘at the equator of the seed. 
-Jour. Straits Brarch R. A. Soc., No. 86 1922. 
