NOTES ON DIPTEROCARPS. 287 
figure 9 one in which a lobe of the outer cotyledon has suffered 
injury (the arrow indicates the place), and its arrested growth has 
given the other lobe and the lobe of the placentar cotyledon in 
contact an opportunity for expansion beyond the normal. That 
this should happen is indicative of the pressure set up within the 
fruit,—the pressure which continued is also the cause of the rup- 
ture of the fruit-wall in germination, however at that period with 
a small amount of altered tension, due to the outer layer of the 
fruit wall contracting in drying somewhat more than the inner. 
In my study of germinating Dipterocarps I have found no 
exactly similar case of a tendency in the ruptured fruit to gape 
and therefore it must be described in detail. The lines of rupture 
are variable in place. as in Jsotoma (vide this Journal above) and: 
are quite clearly brought about by the pressure of the growing 
embryo; but when they have been produced, the drying of the 
outer laver of the fruit-wall continues the tearing and causes the 
split wall to assume the appearance which is represented in figures 
ii and 1 "Wiis is not a hysroscopie action; and thererore 
no soaking of the seed brings the edges of the gaping crack together. 
Obviously it greatly facilitates the escape of the young plant from 
the imprisoning fruit-wall. 
71. 
Figures 10 and 11, sections through the fruit of Shorea Thiseltoni, 
showing the packing of the cotyledon-lobes, and the places where in these 
cases the fruit-wall was split. 
The fruit of Shorea Thiseltoni germinates without resting, 
and in germination the lines of splitting commence at the apex of 
the fruit, and extend downwards. The most usual course of 
events is for there to be three splits, and for two of them to 
extend to the base, whereon a panel of the fruit-wall is free and 
foreed out. This panel is usually rather less than one third of the 
circumference: but there is great variability. The variability is 
accompanied by a great variability in the relative size of the lobes 
of the two cotyledons; and may be considered as a consequence of 
it, as has been suggested in the note upon Jsotoma borneensis ; and 
the most unusual forms of splitting were found to occur with 
unusual twisting or unequal development in the cotyledons. 
The fruits sink in water, and may germinate submerged ;* 
doubtless if such should happen in nature germination would be 
* Lewkowitsch, (Chemical technology and analysis of Oils, Fats and 
Waxes, ii, London, 1914, p. 601) has a statement that submersion of the 
fruits of Dipterocarps is resorted to in Borneo in the preparation of Tang- 
kawang oil because it prevents germination. This reason appears wholly 
incorrect: but submersion by killing the caterpillars and grubs which so 
freely devour the embryo within the fruits may prevent loss in manu- 
facture. 
R. A. Soc., Not 86 1922. 
