48 SIR DIETRICH BRANDIS—AN ENUMERATION 
the irregular masses of xylem and phloàm that constitute the 
central cylinder, while two on the edges in the underside of 
the petiole are situated outside the central cylinder. This 
remarkable peculiarity—that some of the resin-ducts in the 
petiole are outside the central cylinder—is found in all species 
of this genus, as far as they have been examined. Fig. 6 is a 
section of the petiole, a short distance above its base. 
These 5 resin-ducts continue through the entire length of the 
petiole to the base of the blade and into the midrib. In the mass 
of xylem and phloém, with pith between them, which forms the 
central cylinder at the base, two portions may be distinguished—- 
viz. on the underside of the petiole a semicircle of xylem with 
a belt of phloém on the outside, and pith on the inside, the 
latter enclosing a large resin-duct; and secondly, on the upper 
side of the petiole straight bands of xylem and phloém with pith 
between, bent downward at the ends, so as to overlap the semi- 
circle on the underside. Enclosed in this mass near the ends are 
the two upper ducts, while the two lower resin-ducts are outside 
the central mass of vascular bundles. Below the base of the blade 
there is on the underside an outer semicircle, though here and 
there interrupted, of xylem with a belt of phloém on the outside, 
in the pith of which is always the central resin-duct, and some- 
times also two of the lateral ducts, while the two others are always 
outside the central cylinder. The semicircle is closed, but not 
completely, by a bar of xylem with phloém on the outside. A 
ring is thus formed, and this ring encloses several curved bands. 
of xylem, each with a belt of xylem on the underside, the opening 
of the curve looking towards the upperside of the petiole. 
Broadly speaking, the structure here described of D. lanceolata 
represents the structure of all species, as far as known, with 
some variations, which will now briefly be noted. In D. aro- 
matica the base of the internode generally has one main resin- 
duct in the centre of the pith, which sends out branches at 
a higher but varying level. In some cases, however, the main 
duct has already divided at the base of the internode, so that in 
these cases 2 or 3 ducts appear at that point. The lateral leaf- 
traces enter the bark at varying levels, in some cases above the 
middle of the internode. After the branch-ducts, which are 
destined for the apical leaf-trace and for the axillary bud, have 
separated from the main duct, this subdivides, sending off, first 
one, then a second branch for the lateral leaf-traces of the next 
