18 SIR DIETRICH BRANDIS—AN ENUMERATION 
The lateral traces leave the central cylinder at a higher level, and 
do not enter into the leaves, but into the stipules. Here, there- 
fore, the apical precedes the lateral traces, while as a rule the 
lateral precede the apical trace. 
Another peculiarity of Dipterocarps is, that there are resin- 
ducts in the pith of the internode and of the leaf-traces. These 
resin-ducts, being exceedingly prominent on transverse sections, 
first attracted the attention of anatomical botanists. In Dryo- 
balanops there is one main duct in the centre of the pith, sending 
out branches at different levels, so that in a transverse section 
several ducts as a rule are seen. This genus has another peculi- 
arity, that the lateral leaf-traces often run through the bark 
for an entire internode. On good herbarium specimens these 
cortical leaf-traces may be readily distinguished as longitudinal 
raised lines (Plate I. fig. 17), and a good lens shows the distribu- 
tion of the resin-ducts on a transverse section. 
In the other genera the resin-ducts are on the circumference 
of the pith, and they are more numerous. These ducts send 
branches into the leaf-traces, both into the apical and lateral. 
For this purpose the duct has to make its way through the belts 
of xylem and phloém which enclose the pith. The first change 
noticed is, that the medullary rays of the xylem arrange them- 
selves like the rays of a fan (Plate I. figs. 4, 5, Dryobalanops). 
The further progress through the wood may be seen in fig. 8 
(Hopea cernua), and in the case of stipular traces in figs. 11 and 
12, Dipterocarpus alatus and pilosus. It is a remarkable fact, 
which I have observed in all species of this order examined by 
me, that of two corresponding lateral leaf-traces one is always in 
advance of the other, both are never in exactly the same stage. 
The figures on the Plates which accompany this are not suffi- 
ciently magnified to show this remarkable feature in all instances. 
Fig. lof Plate I., however, clearly represents the left-hand lateral 
trace in advance of the other. In addition to the ducts which 
Cho aer Bud. A ane vpular traces a number also go into 
central cylinder. or even before th peti " S irom ta 
the central cylinder narrows info a ne v^ ue Hd 
resin-duets (Plate I. fig. 10, Shorea obtusa) ve Ë e e i 
branch off from this neck ‘and trai h MEM 
into the axillary bud. The number us MN sao wa 
genera which have them in the circumference of the pit — 
of the pith varies 
