282 NOTES ON DIPTEROCARPS. 
Fig. 2. Embryo of Isoptera borneensis seen from the end showing 
the outer cotyledon folded over the placentar cotyledon. 1% nat. size. 
The vitality of the seed is not great. The fruit floats and 
germinates floating if the purpose of floating has not been achieved. 
by a stranding in some new spot. Probably the end of germinated 
floating fruits arrives very quickly and the seedling perishes: it is 
beavier than water, and falling from the fruit sinks. 
In germination the fruit-wall ruptures at no constant place, 
but in response to the pressure of the variable young plant within 
and not at any weak hnes in the wall. Here are four diagrams. 
Figs. 3—6. Diagrams of the position of the cracking of the fruit- 
wall in the germination of the seed of Jsoptera. borneensis, No. 3 is the: 
most usual way. No. 4 is not uncommon being No. 3 as it were incom- 
plete; No. 5 is No. 4 oblique,; No. 6 is the reverse of No. 3. 
showing the cotyledons in transverse section: the outer cotyledon 
in eermination has a tendency to flatten’ itself, which tendency 
pushes chiefly right and left, and is fortified by a similar tendency 
in the inner or plac entar cotyledon; this results further in a second 
direction of pressure,—towards the part of the wall where the 
placenta is, i.e. upwards in the diagrams. Under these pressures 
the wall gives way, first as a rule on the right and on the left, 
and either later near the placenta, or (diagram 4) not at all. The 
commonest form of sphtting is that in diagram 3, the third, last 
and often not extensive, crack being close against one side of the. 
attachment of the placenta to the wall. 
In diagram 5 is a case where the lobes of the placentar 
cotyledon were unequal and the splitting unusually oblique. 
If the fruit is spht into two, as in diagram 4, the two parts 
are nearly halves. Here are appr oximate measurement in degrees. 
of, a circle of six fruits split into,two:— 
ses placenta attached about the middle of the smaller part.. 
ae placenta attached about the middle of one of the parts.. 
SO 
171° placenta attached about the middle of the larger part. 
Jour. Straits Braneh 
