466 DR. ERIC DRABBLE ON THE 
separated from one another by only a single layer of cells. Through this portion of the 
cortex run lignified fibres, usually singly, sometimes in pairs, but never in bundles. The 
innermost zone of the cortex is composed of smaller, more tightly packed cells, without 
fibres or air-spaces. 
"The endodermic cells are lignified and thickened almost equally on all the walls. The 
cells are about four times as long as broad. The pericycle varies from one to two cells in 
thickness; the cells are about three times as long as broad, somewhat lignified and 
pitted. Inside the pericycle comes a broad zone of sclerenchyma enclosing a central 
parenchymatous pith. In this zone the xylem and phloem are embedded. 
The majority of the xylem-groups consist of a few protoxylem-vessels followed internally 
by a single large vessel, but sometimes the large vessel is wanting, or represented by only 
a comparatively small structure. 
(25) Raputa Hoor", C. Mann & H. Wendl. 
"The limiting-layer consists of thin-walled isodiametric cells which are cuticularized and 
slightly lignified. "This is followed by about six layers of slightly lignified small fibrous 
cells, succeeding which internally is the parenchymatous inner cortex, the external 
layers of which are composed of smalltightly packed cells. The middle layers consist of 
larger cells with large air-spaces arranged in many series, and bundles of fibres provided 
with well-developed stegmata. Immediately outside the endodermis are two or three 
Jayers of cells without air-spaces, but with bundles of fibres, which here approach much 
more closely to the central cylinder than is usually the case. 
The endodermie ceils are elongated and fibrously thickened and lignified as usual, and 
the lumina are largely occluded. 
The pericycle is one or two cells in thickness, consisting of cells about twice as long as 
broad, slightly lignified and minutely pitted. The ground-tissue of the central cylinder 
is sclerenchymatous, and generally extends to the centre, no pith being developed. In 
other cases there is a lignified central tissue distinct from the sclerenchymatous zone, 
and containing a few non-lignified elements. It is seen as a distinct tissue when the 
section is treated with sulphuric acid. 
The protoxylem-vessels are succeeded internally by a series of vessels gradually 
increasing in size, the innermost nearly reaching the centre of the root. The peripheral 
xylem-groups form V’s and enclose the phloem-groups. Occasionally a xylem V encloses 
a phloem V, and this, again, a small xylem-group. | 
(26) METROXYLON Sacu, Roxb. 
The limiting-layer is exceptionally well preserved and consists of thin-walled 
isodiametric lignified elements. This is succeeded by a zone of more or less square-ended, 
elongated, lignified, pitted cells, and this again by the parenchymatous inner cortex with 
an irregular development of air-spaces, and strands of fibres bounded by stegmata. The 
cells of the endodermis are very greatly thickened and the lumina almost occluded. The: 
lignified pericycle is two elements in thickness; the inner cells are, however, much 
reduced opposite the protoxylem. The whole of the ground-tissue of the central. 
