ANATOMY OF THE ROOTS OF PALMS. 459 
the cells much thickened on all except the outer tangential walls. They are considerably 
elongated and the thickening is of a * fibrous ” nature. 
The pericycle comprises one or two layers of lignified pitted cells. The xylem-plates 
and the phloem are embedded in a sclerenchymatous zone. The xylem forms very wide 
V's, and internally are vessels that appear to have no relation to the xylem-plates. 
There is a small pith, chiefly occupied by two strands of sclerenchyma, connected 
externally with the sclerenchyma-zone. In the centre of each is a single vessel. 
In a more proximal portion of the root the outer subperipheral elements are separated 
from those more internally placed by several layers of unaltered parenchymatous cells, 
This means that the centripetally proceeding lignification has not yet met that proceeding 
centrifugally. 
The internal cortex, as in {the more distal region, contains very irregular air-spaces 
and many fibres scattered singly. 
On one side of the central cylinder the sclerenchymatous zone is interrupted, and at 
the same point the endodermis, instead of completing the circle, dips in very deeply, 
forming a groove occupied by cortical ground-tissue. Down the sides of this groove the 
endodermis is continuous, but towards the base it becomes broken up, and at the very 
bottom is wanting as a specially differentiated layer, so that the ground-tissue internal 
to (** medulla ") and external to (“ cortex ") the sclerenchymatous zone is continuous. 
The general structure of the central cylinder is the same as that in the more distal 
portion described above, but there are many more medullary sclerenchymatous strands, 
some of which are completely separated from the sclerenchymatous zone enclosing the 
medulla. In the centre of each medullary strand is a single vessel. 
(8) ConvPHA AUSTRALIS, R. Br. 
The limiting-layer consists of almost isodiametrical thin-walled lignified cells, most of 
which are exfoliated—exposing the underlying layers of thiek-walled, elongated, pitted 
cells, which are only slightly lignified. Following this zone is one of some six or seven 
cells in depth, composed of parenchyma. Then comes a zone of elongated, square- 
ended cells, comparatively slightly lignified, and passing gradually into a large-celled 
parenchymatous inner cortex, with very irregular air-spaces and many scattered lignified 
parenchyma-cells with thick pitted walls. No fibres are present in the cortex. In the 
innermost zone the air-spaces are absent, but there is much lignified parenchyma. 
The endodermal cells are about four times as long as broad. Some of these are 
thickened and lignified on all but the outer tangential walls ; others are thin-walled and 
slightly cuticularized. 
The pericycle, usually two cells in depth, is parenchymatous. | 
The ground-tissue of the central cylinder is composed chiefly of cellulose-walled paren- 
chyma, but intermingled with it are many lignified sclerenchymatous elements. 
'The protoxylem-vessels are lignified, but the larger internal vessels retain their 
cellulose walls. 
` Occasionally a V is formed enclosing a phloem-group. 
— In the centre of the root is a thin-walled, parenchymatous pith, in which are air- 
SECOND SERIES.— BOTANY, VOL. VI. J-U 
