8 SIR DIETRICH BRANDIS—AN ENUMERATION 
places far into the plains, as well as on the hills of Central 
India from the Ganges to the Godavery river. 
14. Shorea obtusa, Wall.—In Burma scattered, chiefly in forest 
of Dipterocarpus tuberculatus ; in Cambodia forming pure 
forests (Pierre). 
15. S. Balangeran.—Gregarious upon the banks of the Pattai 
river, Borneo (Korthals). 
16. S. hypochra, Hance.—Gregarious in Cochinchina (Pierre). 
17. Vatica obscura, Trimen.—Gregarious in the Eastern pro- 
vinee of Ceylon (Zrimen). 
Those species which do not grow gregariously, though they 
may be common, occur as isolated individuals, often at con- 
siderable distances apart. The number of these is much 
greater than the number of gregarious trees. Yet many of 
them, such as Kanyin, Dipterocarpus alatus, flower and seed 
abundantly. A remarkable fact is, that of the large number of 
seeds of this species which were sent to me in alcohol from 
Burma very few were perfect, many were worm-eaten, while 
in others in the place of the embryo the fruit-cavity was filled 
up by a dry tissue resembling cork. I mention this fact, because 
two Indian species of Anogeissus, A. latifolia and acuminata, 
show the same peculiarity. Among large quantities of seed 
which I examined when studying Combretaces a few years ago, 
I only found a few with a perfect embryo. These trees produce 
seed abundantly every year, and yet they are not gregarious; 
but, like Dipterocarpus alatus, occur singly in mixed forests. 
The circumstances, which enable certain species in tropical or 
subtropical countries to form pure, or nearly pure forests will 
prove an interesting subject of biological research for those 
whose good fortune enables them to study these trees in their 
native forests. 
It is a remarkable fact, that two natural orders of trees, 
Conifere and Dipterocarpaces, many species of which form 
nearly pure forests of large extent, form resinous substances on 
a large scale in their leaves and deposit them in the wood. A 
complicated system of resin-ducts is found in all parts of Dipte- 
rocarps a8 well as of Conifers. In the living tissue these sub- 
stances are in a liquid oily condition ; while in the old wood solid, 
in Dryobalanops crystalline, masses are deposited. It is beyond 
the scope of the present paper to enter into detail upon this 
important subject. In regard to Dryobalanops, I must refer the 
