4 
Lang.—Studies in the Morphology and 
a continuous line, the phloem by a dotted line internal to this. The outer 
and inner metaxylems are represented by two sets of radially directed lines ; 
between them the protoxylem elements occur in groups, and are represented 
in black in relation to the leaf-trace, but are usually not specially indicated 
in the rest of the stele. Though diagrammatic in the representation of the 
tissues, these figures are based on camera-lucida drawings, and represent the 
position and extent of the various tissues as accurately as possible. 
It will be evident that the inner metaxylem is least strongly developed 
at the ventral side of the stele. The greater thickness of the xylem-tube 
Text-fig. i. a. Section across adult"rhizome near to the growing region, showing the attachment 
of the roots and their relation to the cortex. Only the outline of the stele and the outer limit of the 
xylem are indicated. B. Similar section through mature region of the rhizome. The stele of the 
rhizome shows a departing leaf-trace to the left of the median dorsal line, and the disturbance in 
relation to a vestigial bud on the left. There is an internal endodermis in the base of the root, 
unconnected with that in the rhizome, l.sh., leaf-sheath; R, roots; xy xylem ; px., protoxylem; 
x.o.y outer xylem; x.i., inner xylem; l.t., leaf-trace; dr'., vascular disturbance for vestigial bud; 
e., outer endodermis ; e.i ., internal endodermis of rhizome ; e.i.r., internal endodermis of root. 
dorsally is mainly, though not entirely, due to the greater development of 
inner xylem there, especially in relation to the vestigial bud. 
Proportions of inner and outer metaxylem. In rhizomes of the adult 
type both xylems are always represented, but the degree of development of 
the inner xylem exhibits a wide range of variation. In large rhizomes, 
such as that just described, the inner xylem is well developed; a portion of 
the vascular tube of this type is shown in PI. I, Photo i. The tracheides 
of the outer xylem often show some indication of radial seriation, but this 
is to be related to the sequence of divisions in the procambial stage, and 
does not indicate a secondary development. The xylem in all normal 
rhizomes examined is wholly primary, though an anomalous secondary 
development will be described below in relation to the branching of the 
rhizome. The inner xylem is usually much less marked in smaller 
