484. DR. ERIC DRABBLE ON THE 
of that surface presented to the exterior of the root. The portion of this cylinder 
presented to the interior of the root is composed of a number of isolated small fibrous 
masses with endodermis on the surface nearest to the centre of the root. Each of these 
fibrous masses has a radially symmetrical development of xylem and phloem. 
The fibrous tissue is throughout usually in the form of wedges. 
In the parenchymatous tissue occupying the interior of this cylinder are many fibrous 
masses each with xylem and phloem generally radially arranged in several groups. 
Accompanying this incomplete cylinder are three complete cylinders, round each of 
which the endoderm is continuous. The whole arrangement in this root is of great 
interest as bearing on the question of the morphological value of medulla and cortex in 
these organs. The general ground-tissue in which the cylinders are embedded is provided 
throughout with well-developed bundles of fibres and air-spaces. 
(58) Cocos PLUMOSA, Hook. 
The tegumentary layers are normal. A thin-walled layer of isodiametric, slightly 
cuticularized cells is followed by a more than usually broad zone of small elongated 
elements, only slightly lignified, and this again by the parenchymatous inner cortex with 
small and very irregular air-spaces. 
Immediately surrounding the endodermis is à narrow zone of thick-walled and pitted 
stone-cells. The endodermis is lignified, and the pericycle two cells in thickness except 
just opposite to the protoxylem, where it is reduced to one cell. Opposite the phloem the 
inner pericyclic cells are often considerably crushed, but seem to be always present. A 
broad zone of fibrous tissue carries the xylem and phloem and surrounds a central pith. 
There is a well-developed system of scattered internal vessels which do not extend to the 
inner margin ofthe fibrous zone. V-formation is very general by the approximation of 
two xylem-groups to the exterior of one large internal vessel. The phloem-groups vary 
greatly in outline, from small peripheral circular patches to radially elongated internally- 
stretching bands. 
In larger roots the inner vessels are much more regularly arranged, usually in two 
rings. Others occur in fibrous masses distributed in the medulla. Some of these 
strands are connected externally with the fibro-vascular cylinder, but the majority 
are free. 
In still larger roots the medullary fibrous groups are more abundant and more than 
one vessel may occur in each. Wedge-formation also obtains in the fibrous zone, which 
is interrupted by a wide gap on one side, the free edges being incurved. The asymmetry of 
the xylem-groups is here not so marked as usual, internally pointing protoxylem-groups 
being found. - 
_ The phloem, however, tends to retain its outward orientation. Just inside the gap 
| are two little cylinders, with xylem and phloem radially arranged, one being almost 
* completely surrounded by endodermis. The other little group, which lacks internally 
arranged protoxylem, lacks also internally developed endodermis. 
