2 
Lang—Studies in the Morphology and 
While this general reference to previous investigations on the rhizome 
of Helminthostachys will be sufficient, the main structural features, which are 
matters of common knowledge, may be briefly summarized. The horizontal, 
subterranean rhizome is definitely dorsiventral. The leaves, alternating 
with one another, arise in two dorso-lateral rows, while roots spring from 
the lower side and the flanks of the rhizome. The basal region of each 
leaf forms a peculiar sheath, which covers over the next younger leaf, and 
is broken through on the expansion of the latter. The narrow canal leading 
to the deeply seated vestigial bud continues backwards and inwards from 
the axil of the sheathing leaf-base. The rhizome has a wide parenchyma¬ 
tous cortex. The stele is tubular, but is not a solenostele, since there is no 
trace of internal phloem. It is bounded by the outer endodermis, within 
which come in order pericycle, phloem, conjunctive parenchyma, xylem, 
and pith. An internal endodermis abutting closely on the inner surface of 
the xylem is usually present in large rhizomes; it may be more or less 
incomplete, or wanting. 
The cells of the pith resemble the cortical cells, and like them are often 
packed with starch. Cells with peculiar contents, recognized by Campbell 
as corresponding to the tannin cells of the Marattiaceae, may occur in pith 
and cortex. The xylem in adult medullated rhizomes is characteristically 
mesarch. Both outer (centrifugal) and inner (centripetal) xylems are well 
represented, their distinction being easy, as the mesarch protoxylem is often 
well marked. The vascular strands of the roots are attached to the sides 
or lower face of the stelar tube, while the upper side of the latter is dis¬ 
turbed by the departure of the alternating, mesarch leaf-traces. Each trace 
leaves a long narrow gap in the stelar tube ; this usually closes just before 
the next leaf-gap is formed. A further complexity on the dorsal side of 
the tube results from a disturbance of the xylem in relation to each vestigial 
axillary bud ; this is found, as a rule, just as the corresponding leaf-gap 
closes. The rhizome of the young plant shows a similar disposition of 
leaves and roots. Owing, however, to its more slender configuration and 
smaller stele, the leaves, though really in two rows, appear to spring in 
a single dorsal line. The stele may have a solid cylinder of xylem, or may, 
almost from the first, show a small pith. No definite leaf-gaps are left on 
the departure of the early leaf-traces, but a vestigial bud occupies the usual 
axillary position in relation to each leaf-trace. The transition from the 
slender rhizome of the young plant to the full size and usual structure 
appears to be a gradual one. 
This summary of familiar facts will be sufficient introduction to the 
more critical consideration of some particular features of the rhizome of 
Helminthostachys . The difficult questions relating to the apical develop¬ 
ment and its relation to the segmental arrangement, indicated in the 
succession of the leaves and at least suggested by that of the roots, will 
