26 
Lang.—Studies in the Morphology and 
it separates from the xylem of the stele (PI. Ill, Photo 31), the outer 
xylem becomes at once complete around the inner xylem. A little further 
on (PL III, Photo 32) the leaf-trace and stem-stele are still enclosed by the 
common endodermis, but the xylem of the leaf-trace has become completed 
adaxially, in a similar fashion to what has been seen in larger rhizomes. 
The xylem of the stele is almost solid, with outer xylem surrounding a small 
central core of inner xylem mixed with parenchyma. This condition is 
maintained for some distance after the trace has definitely separated from 
the stele, as is shown in PI. Ill, Photo 33, where the section passes through 
the vestigial axillary bud (v.) in relation to the departed trace. The stele 
already shows the first indication of the position of the protoxylem for the 
second leaf-trace. The xylem of this trace is seen still forming part of the 
stele in PI. Ill, Photo 34, and it will be evident that a small definite pith is 
present, the inner xylem being practically replaced by parenchyma. It is 
unnecessary to follow the anatomy of this branch node by node, especially 
as it showed no further advance towards the adult type. Indeed, after the 
departure of the second leaf-trace, the stele, though usually showing a small 
pith, was smaller than at the base of the branch, and more like that of 
a young plant. 
While the departure of the first leaf-trace from the stele of the first 
branch has now been examined in transverse section, the corresponding 
region of the second branch was shown in longitudinal section. The general 
relations of the inner and outer xylems of this branch to the stele have 
already been described and discussed. As shown in PI. II, Photo 29, the 
base of the branch had a well-developed outer xylem composed of pitted 
tracheides, and centrally a * mixed pith *, consisting of narrower tracheides, 
with spiral and reticulate markings, and rather abundant parenchyma. 
The same structure was traceable as the stele became more slender, and 
it was evident that this branch, while corresponding in the position of inner 
and outer xylem to the first branch, tended to have the inner xylem 
largely replaced by parenchyma. It was possible to prove also, from the 
longitudinal sections, that the leaf-trace departed from the outer xylem 
only, and that the stele was to be regarded asmesarch. PI. Ill, Photo 35, 
shows the base of the departing leaf-trace, and it will be clear that while 
a gap is left for some distance in the cylinder of outer xylem, the inner 
xylem (#.*.), consisting of long spiral tracheides, can be traced straight 
on within this gap, just as it can on the lower side of the stele. The 
behaviour of the inner xylem here is thus essentially similar to what held 
for the first branch, allowing for the fact that in this case more medullary 
parenchyma is present. The facts seem inconsistent with regarding the 
centrally placed tracheides as protoxylem, while they agree with regarding 
it as the representative of the inner xylem, a view which its basal connexion 
has already suggested. 
