12 Lang.—Studies in the Morphology and 
the trace completed adaxially before it had separated from the stelar 
xylem. In this case there was no difficulty in the interpretation, since 
the inner xylem first disappeared from within the nascent trace. In the 
trace figured the adaxial xylem is almost complete, and is well represented 
on the left side. 
The variety shown by the leaf-trace in different pieces of rhizome of 
Helminthostachys is remarkable, and has necessitated the description of 
a number of examples. A general plan will, however, be seen to underlie 
the variety. The xylem of the trace is ultimately equivalent to, and derived 
from, an arc of the outer xylem of the stelar tube. No inner xylem may 
be continuous into the trace, or the latter may be mesarch at its base, the 
inner xylem dying out sooner or later. The outer xylem tends to be 
completed adaxially (though this does not always take place); the resulting 
construction is essentially distinct from mesarchy as we find it in the stelar 
tube of the xylem. In preparation for division the protoxylem separates 
into two groups, and the trace passes through a clepsydroid stage that is 
often clearly marked and striking. The monarch pre-clepsydroid condition 
may, however, persist until the trace leaves the rhizome. More usually the 
trace has divided twice before this takes place, the complex vascular system 
of the petiole being thus continued backwards into the cortex of the 
rhizome. In all cases observed, however, the trace is monarch as it separates 
from the stele, though the continuation backwards of the double condition 
seen in the clepsydroid stage would be a readily comprehensible term in the 
series of variants. 
Parallel variants in the structure and relations of the leaf-traces will be 
referred to below in considering more slender rhizomes showing juvenile 
structure, and the whole question will be discussed at the end of the paper. 
The vascular disturbance in relation to the vestigial buds. The original 
description by Gwynne-Vaughan 1 of the structures which must undoubtedly 
be regarded as vestigial or dormant lateral buds, or rather apices, was illus¬ 
trated by clear diagrammatic figures. These show the course of the narrow 
canal extending backwards and inwards from the axil of a leaf-sheath to the 
neighbourhood of the stele just in front of the closed leaf-gap corresponding 
to the subtending leaf, and also the disturbance of the stele in relation to 
the vestigial structure. As his figure shows, the canal turns slightly forwards 
at its lower end, and, so far as I can judge, the dormant apex is situated 
behind this inner portion. As regards the structure of the vestigial bud 
itself, I can at present add little to Gwynne-Vaughan s account. It seems 
to consist only of a dormant apical meristem, the structure of which is 
difficult to make out in the absence of segmentation. It is of some interest, 
for comparison with the main apex, to find that the lower portion of the 
canal may be enlarged by the development of hairs projecting into it. 
1 Loc. cit., p. 171, Fig. 19. 
