284 NOTES ON DIPTEROCARPS. 
As far as is known, it is universal for the Dipterocarps to 
possess in the ovary three chambers and six ovules, two in each: 
one ovule only in all normal cases matures. One flower only, shall 
we say, in 10,000 matures fruit. It is remarkable then, that the 
production of the six ovules to each flower should be so constant, 
and it suggests an ancestry which had not winged fruits as so many 
modern Dipterocarps have, because six seeds carried away together 
on the wind would be tooheavy a load for efficient wind-distribution 
and, settled together, would compete unprofitably. Wind-distri- 
bution appears, therefore, a less ancient phenomenon than their six, 
ovules, but yet it is so general as to be characteristic of the order. 
It is easiest to consider it as co-aeval in the order with its separ- 
ation from something more ancient, and to consider the absence 
of it to be subsequent or secondary. Jsotoma has lost it—has 
taken to water-distribution as an alternative. Vatica Wallichu has 
done the same. Some species of Shorea such as S. Thiseltoni, 
some of Dryobalanops, some of Vatica, the species of Balafocarpus, 
and the species of Pachynocarpus hold their own producing fruits 
very heavy for wind to hft them, and are distributed through small 
distances by being rolled or carried along the floor of the forest. 
They too have lost their wings. If we think of the evolution of the 
order as suggested it is of the. greatest importance to understand that 
the s] slitting of the fruit-wall is not along definite lines, that is to 
say ‘he is in it no sign of a pre-Dipterocarp dehiscent condition 
when six seeds might mature and need for the sake of efficiency that 
they be scattered singly. 
Against this line of argument it has to be admitted that some 
species of the genus Vatica possess weak hnes in the walls of 
their fruits where rupture occurs. The lines seem tertiary how- 
ever, and are being studied. 
The cotyledons of Isotoma borneensis contain chlorophyll in 
abundance before germination, and on germination are exposed to 
to the hght and held, like the coty ledons of most species of Shorea, 
upon short petioles. 
(OD) 
