AGL DR. ERIC DRABBLE ON THE 
clements alone are lignified, the inner vessels being quite thin-walled and retaining their 
cellulose nature. There is a central non-lignified parenchymatous pith with irregular 
air-spaces formed by disintegration of cell-walls. 
In other cases the xylem and phloem are embedded in lignified sclerenchyma, the 
vessels are all lignified, and there is a very small pith in the centre. 
(20) SABAL FILAMENTOSA, H. Wendl. 
The limiting-layer is of the usual type and is succeeded by a zone of clongated 
lignified elements, generally square-ended. These are followed by the parenchymatous 
inner cortex with air-spaces in three or four irregular circles and separated from one 
another by diaphragms only one cell in thickness. In this region occur lignified cells 
which may be isodiametric or elongated. No fibres are present. The cells of the 
endodermis are so strongly thickened and lignified on all but the external tangential 
walls that the lumina are almost occluded. 
The pericycle varies from one to two cells in thickness; it is generally lignified, but 
some of the cells retain their cellu.ose nature, the cellulose regions generally occurring 
opposite to a phloem-group. 
The central cylinder is almost entirely occu pied by sclerenchymatous tissue in which 
lie the xylem and phloem. "The phloem-groups extend centrally to a somewhat greater 
extent than usual. There is a double ring of large internal vessels without apparent 
relation to the protoxylem-groups. Centrally there is a very small parenchymatous pith 
consisting in transverse section of four or five elements only. 
II. BORASSIN X. 
(21) HYPHÆNE THEBAICA, Mart. 
The limiting-layer is exfoliated. Peripherally there is a dense zone of lignified 
elements. This is followed by the parenchymatous inner cortex with small irregular 
air-spaces and individual lignified parenchymatous elements and bundles of very thick- 
walled and pitted fibres. The endodermic cells are thin-walled, non-lignified, and non- 
cuticularized. The partially lignified pericycle is one or two cells in thickness. There is 
a ground-mass of sclerenchyma in which lie the xylem and phloem. A single ring of 
large vessels lies internally to the protoxylem-groups, and these form the apices of 
irregular Va, Two adjacent phloem-groups also frequently converge centrally and may 
form a phloem V, the arms of which enclose a small xylem-group. In other cases an 
isolated phloem-group occupies the apex of the phloem V, and the arms instead of being 
continuous with this are separated from it by portions of the sclerenchymatous tissue, In 
the centre of the root is a parenchymatous pith, largely occupied by sclerenchymatous 
strands each enclosing a vessel; usually the vessel is placed quite laterally in the strand 
instead of in the centre as in most roots. Some of the strands are connected Jaterally with 
the sclerenchyma-zone. 
