266 
A. G. Tanstey, 
It is most convenient to begin with the monotypic gdnus 
Helmintliostacliys , confined to the Indo-Malayan region, and with 
the most complicated leaf-segmentation found in the group. 
The rhizome is subterranean, creeping and dorsiventral, bearing 
two rows of leaves on the upper surface, and numerous roots on the 
lateral and ventral faces. It contains a hollow cylindrical vascular 
skeleton (Fig. 92, A, Fig 93), with a ground tissue pith continuous 
with the cortex through the leaf-gaps, but no internal phloem. An 
Fig. 93. Helmintliostacliys zeylanica. Diagram of transverse section of 
stele showing departure of leaf-trace (above) and root-stele (to left). 
internal endodermis is present which is irregular and often inter¬ 
rupted, suggesting reduction. The xylem is mesarch, with spiral 
protoxylem, and the tracheids of the metaxylem possess highly 
developed bordered pits. The leaf-trace departs as a single curved 
mesarch strand, and leaves a well-marked elongated leaf-gap. The 
trace splits almost at once into strands symmetrical about the 
vertical plane, and each of these again divides into two, so that four 
strands, which are diagonally arranged and have crescentic endarch 
xylems enter the petiole. Each of these again bifurcates, giving rise 
to four diagonal pairs of bundles, the members of each pair being 
turned towards one another (Fig. 94). The eight bundles become 
equidistant and undergo some further splitting, increasing in 
number to ten or twelve. The bundle representing one free end of 
the typical leaf-trace curve becomes specially large, and gradually 
sinks into the centre of the petiole, where it turns round so that its 
protoxylem faces adaxially (Gwynne-Vaughan ’05). Branches from 
this internal strand pass out to the pinnae. The vascular supply of 
the fertile spike is derived from the two middle strands on the upper 
