182 BOTANICAL GAZETTE [MARCH 
fuses with it. At other times, a long narrow slit may occur in the 
cylinder. Some of the gaps are relatively large, measuring 0.6X 
o.7mm. Apparent gaps, due to a failure of the xylem parenchyma 
to lignify, sometimes occur; in these the phloem is not interrupted. 
In most of the incidental gaps, however, the cortical parenchyma 
connects with that of the pith, as in leaf and root gaps. 
Lignification occurs first in the layer of tracheids nearest the 
pith; these first xylem elements differ in no way from those outside. 
They are true tracheids, often very irregular in shape; lobed and 
even branched forms occur. They are relatively short, 3-6 times 
as long as broad; the walls are reticulately thickened. The ligni- 
fication does not begin at definite points, but indiscriminately 
throughout the inner layer. It proceeds in an outward direction; 
in the mature stems the xylem is 5 or 6 tracheids in thickness. 
Occasional irregular divisions occur within the procambium strand 
after lignification has begun, but there is no true secondary thick- 
ening. 
The phloem is uniformly a single layer of cells; it is separated 
from the xylem by a layer of parenchyma 3-5 cells in thickness. 
There is no endodermis except in the extreme basal region and at the 
points of attachment of roots; in these instances it is a mere exten- 
sion of the root endodermis, and is not to be considered as related 
to the stem stele. The phloem abuts directly upon the cortical 
parenchyma composed of large spherical or ellipsoidal cells with 
intercellular spaces; the cells of the layers next the phloem are some- 
what smaller than those farther out. The walls of all the cortical 
cells are secondarily thickened with cellulose, as in the inner region 
of the root cortex; the pits are much larger. The pith is in all 
respects similar to the cortex; the cells of the layers next the xylem 
are considerably smaller than the average. There is no starch 
storage in any part of the plant, but fats occur in some quantity 
in all parts, especially in the pith and cortex of the stem. The 
growth of the stem is by a tetrahedral apical cell, as in other species 
of the genus; its segmentation was not examined. 
The largest rhizome of the Australian material presents 4? 
interesting variation of this usual situation. The base has decayed 
and it is impossible to say whether the stem originated from 4 
