50 
Lang.—Shi dies in the Morphology and 
usually at the level of the separation of the next leaf-trace, but is sometimes 
further forwards and in smaller rhizomes nearly always further back. 
6. The vascular relations of two branches, developed from lateral buds, 
to their parent rhizomes are described, and place the nature of the dormant 
buds beyond doubt. 
The xylerri of the stele of the branch is composed of a central strand 
of tracheides of the inner xylem surrounded by a zone of outer xylem. The 
inner xylem is continuous with the corresponding tissue of the main stele, 
while the outer xylem of the branch is continuous with the outer xylem of 
the rhizome, or rather with a secondary development of this, to which the 
name ‘ accessory xylem ’ has been given. 
This accessory xylem has the characters of an irregular secondary 
thickening of the stele of the rhizome, and may be developed not merely in 
the direct tract backwards of the branch stele, but all round the main stele 
and before and after the branch departs. 
7. The inner xylem is unequally developed at different levels in the 
adult rhizome, and exhibits a regular rhythm of decrease and increase in 
the dorsal region of the stele. It diminishes or disappears opposite the 
nascent leaf-trace, and is especially strongly developed as the leaf-gap closes. 
A corresponding rhythm is traceable in slender juvenile rhizomes. 
The inner xylem may be largely replaced by parenchyma before a leaf- 
trace begins to separate, but increases again in amount as this happens, 
bridging across the gap left in the outer xylem by the departing trace. In 
small rhizomes this increased development of the inner xylem may lead to 
the stele becoming solid on the departure of a leaf-trace, to become 
medullated again as the next trace is initiated. 
8. The structure of slender rhizomes with the juvenile type of stele is 
described both for plants developed from the embryo and for branches. 
These show essential agreement, with differences in detail depending partly 
on the strength of the shoot, and partly on the earlier or later development 
of a pith by replacement of most of the inner xylem by parenchyma. 
The inner xylem in the young plant and the slender basal region of 
the branches consists of spirally thickened tracheides, and histologically 
resembles protoxylem. Its real nature is shown when the true protoxylem 
is distinguishable between outer and inner xylem in relation to a nascent 
leaf-trace, and by the behaviour of the inner xylem at the separation of the 
trace. That the more central xylem of the branch, in spite of its histological 
characters, is to be regarded as inner xylem is further shown by its con¬ 
tinuity with the inner xylem of the main axis. 
9. The juvenile type of anatomy may be maintained for many nodes, 
and no example showing the transition from the seedling structure to the 
adult type has been studied. Rhizomes of different sizes show, however, 
that the change from the juvenile type of structure to the adult condition 
