6 SIR DIETRICH BRANDIS—AN ENUMERATION 
subject to much variation. Notable exceptions are the groups of 
Dipterocarpus indicus and turbinatus, of D. alatus, costatus, 
acanus, and scaber, of Shorea Talura, cochinchinensis, and Jori- 
bunda, and in Vatica (Synaptea), a group of trees found over the 
whole Eastern peninsula from Burma to Cochinchina, V. Dyert, 
grandiflora, faginea, and astrotricha. Further researches may 
possibly prove the existence of two polymorphous species, one of 
Dipterocarpus, the other of Vatica, both with numerous local 
varieties. 
Biological Features. 
The most striking peculiarity of this order is, that numerous 
species are gregarious, forming nearly pure forests of large extent, 
in which one species has obtained the upper hand, to the exclusion 
almost ofall others. In the tropical forests of Eastern Asia these 
species play the part which in Europe belongs to trees of Conifer 
and Cupuliferee—the Scotch Pine, the Mountain Pine, the Spruce, 
and the Beech. The most remarkable of these gregarious species 
is the Sal tree, Shorea robusta, which forms pure or nearly pure 
forests of vast extent at the foot of the Himalaya, from Assam 
to the Punjab, and in the hills of Eastern Central India extending 
south to near the Godavery river. In a climate and on soil 
which suits it, this tree reigns supreme. The most suitable soil 
is either sandstone, as in many parts of Central India, or alter- 
nating beds of shingle and sand, such as are found at the foot 
_ of the Himalaya, or loam resting on gravel and sand. The 
principal factors which enable this tree to maintain the upper 
hand over its associates in a climate and on soil suitable to its 
development may briefly be stated as follows:—The seed ripens 
at the right season of the year, at the commencement of the 
rains, after the forest-fires of the hot season have passed over the 
country ; itis produced in great abundance regularly almost every 
year and germinates readily. The leaves of the seedling plants 
are very large, thus choking other trees and shrubs, which may 
have sprung up with them. When the ground is overrun by the 
jungle-fires of the following season, most seedlings of the previous 
year are strong enough to send up fresh shoots when the rains 
set in, although they may have been burnt down to the root. 
This gives the young Sal plants a great advantage over other 
kinds which germinate at a less convenient season. Again, 
the Sal stands much shade while young, it remains alive for 
