OF THE DIPTEROCARPACE®. 17 
Néerlandaises " (1887), Ann. Jard. Bot. Buitenzorg, vi. p. 145. 
—Prznnz, Flore Forestière de la Cochinchine, tabb. 212-259 
(1889-92).—Herm, Recherches sur les Diptérocarpacées (1892). 
It is not my object in this place to do more than to draw 
attention to a few facts which are useful for the systematie 
treatment of this order. I mean the course of the leaf-traces 
through the stem to the petiole, the distribution of resin-ducts 
in a leaf-bearing internode, and the structure of the petiole. I 
shall say nothing on the present occasion regarding the internal 
structure of the leaf, the seed, wood, bark, root, and other parts 
of the tree. The points in question may best be understood by 
the examination of leaf-bearing internodes, and for purposes of 
comparison petioles should always be examined at the base of 
the blade. 
In common with Lecythidaceez, Ochnaces, and a few other 
orders, Dipterocarps have the peculiarity that the lateral leaf- 
traces and sometimes the apical leaf-trace separate from the 
central cylinder a greater or less distance below the node, 
running through the bark until they enter the petiole. In those 
species where the stipules are broad, stipular traces also are found 
in the bark. As a rule there is one apical leaf-trace and two 
lateral leaf-traces, the stipular traces, if any, separating either 
from the lateral leaf-traces or from the central cylinder. These 
leaf-traces are vascular bundles, either circular, closed all round, 
or open and half-moonshaped, consisting of phloém, xylem, and 
pith, with one, sometimes several resin-ducts in the pith. 
When these leaf-traces separate from the central cylinder, 
the opening of the half-moon is inwards towards the cylinder 
(Plate I. figs. 11, 12, Dipterocarpus). Circular leaf-traces are 
represented on Plate I. figs. 2,3 (Dryobalanops). When the 
lateral leaf-traces bend, preparing to enter the petiole, xylem 
and phloém are directed towards the insertion of the petiole 
(Plate I. fig. 9, Hopea cernua, fig. 10, Shorea obtusa). 
The apical leaf-trace generally leaves the central cylinder at 
the node in order to enter the petiole, while, as already men- 
tioned, the lateral leaf-traces generally leave it at a lower level. 
Stemonoporus, and probably also the other species of Vateriec, 
however, are an exception. Here the apical leaf-trace branches 
off from the central eylinder at a distance below the node, and 
after separating into 3 or 5 separate vascular bundles, runs 
through the bark for some distance before entering the petiole. 
LINN. JOURN.—BOTANY, VOL. XXXI. c 
