Yapp. — Two Malayan ‘ Myrmecophilous ’ Ferns. 199 
though somewhat complicated, is arranged on a perfectly 
definite plan, following the same course through the stem 
as that taken by the aqueous tissue just described. As will 
be seen, the system appears to bear special relation to the 
large conical leaf-cushions which form such a prominent 
feature of the exterior of the stem. 
There is, as mentioned above, a single median, ventrally- 
placed gallery, which runs, in a slightly sinuous course, 
through the whole length of the stem (Figs. 16, 22, &c.). 
This gallery is usually about two or three times as broad as it 
is deep, its floor being convex and its roof concave. At 
regular intervals the central gallery gives off a lateral gallery 
to each branch of the stem, and a vertical one to each leaf- 
cushion. As both the leaves and the lateral branches of the 
main stem are arranged in two longitudinal series, it follows 
that (unless this regularity is interrupted, as it may be, e.g. if 
some of the branches do not develop) there are two series of 
lateral galleries and two series of dorsal ones leaving the main 
gallery. 
One of these lateral galleries originates beneath each leaf- 
cushion, and passes out immediately below a foliar gap, 
through the large gap in the vascular cylinder where the 
branch cylinder (which thus encircles the lateral gallery) 
leaves the main one. It curves slightly as it does so, first 
backwards and downwards and then forwards, finally entering 
a lateral branch, where it behaves like the corresponding 
gallery of the main stem. A second gallery leaves the 
central one close to the point of origin of the side-gallery 
(a, Fig. 20). This travels almost vertically upwards through 
the large foliar gap, and ends blindly in the leaf-cushion, 
under the base of the petiole (Fig. 15). Before entering the 
leaf-cushion, however, it sends out a forward diverticulum 
(Fig. 23) which . passes outside the vascular system altogether, 
by means of the gap in the horseshoe-shaped network of the 
leaf-trace. This diverticulum immediately branches into two. 
One branch (b. Fig. 21) passes outwards, backwards, down- 
wards and finally upwards, ending blindly in the same leaf- 
