ANATOMY OF THE ROOTS OF PALMS. 481 
(54) AnECA Catecuu, Linn. 
(i.) Small root.—The limiting-layer is, as usual, followed by elongated elements with 
dark contents, and these again by a parenchymatous cortex. ‘The outer part of this is 
without air-spaces, but contains lignified elongated elements, with comparatively large 
lumina, and more internally bundles of fibres also occur. In the inner layers of the 
cortex are many large air-spaces in several irregular rings, and in the parenchyma 
enclosing these are large bundles of fibres. The endodermis is lignified and the pericycle 
is two layers in thickness. The fibrous zone in which the xylem and phloem are embedded 
forms a series of bays projecting into the pith. The xylem-elements extend some con- 
siderable distance centrally, und most of the large inner vessels can be definitely brought 
into line with the protoxylem-groups. V’s are often formed, and two protoxylem-groups 
may form a V with the outer of three internal vessels, thus giving a well-marked Y. In 
the pith are some fibrous elements like those of the outer cortex. 
(ii.) In larger roots the pith is much more extensive and the fibrous zone relatively 
narrower. The internal vessels are more scattered and generally lie in sets of two or 
three, or one or two large ones may be accompanied by two or three smaller ones. Into 
both large and small vessels well-developed thyloses project. 
(ii.) In still larger roots, or in sections more proximally placed, the central cylinder 
has a slightly lobed outline. The xylem- and phloem-groups usually lie in threes, two 
xylem-groups or a xylem V and a phloem-group, or one xylem-group and two phloem- 
groups, being embedded in wedge-shaped masses of fibrous tissue, whose apices project 
centrally. ‘The wedges are separated from one another by extensions of the medullary 
parenchyma extending as far as the pericycle (text-fig. 20). The medulla is parenchy- 
matous, and in it are bundles of fibres similar to those of the inner cortex. 
The cylinder is incomplete at one point, and here the endodermis dips in and is lost 
internally, the medullary and cortical parenchyma being continuous. Opposite to the 
gap is a group of fibrous ground-tissue enclosing two vessels. : 
(iv.) In still more proximally situated sections the lobing of the central cylinder is more 
extensive and several gaps are present. Opposite each gap is an internal fibrous strand 
with vessels and in some cases phloem also. ! i 
(v.) In other sections much greater splitting of the central cylinder. is shown, the 
fibrous zone being composed of a number of separate ares of varying size, the ends of 
which are incurved and accompanied by the endodermis, which is eventually lost in the 
eround-tissue. In the smaller segments the fibrous tissue is more and more infolded, 
antl in some cases it fuses internally and a complete ring is produced, only lacking 
endodermis on its central surface. Finally a complete endodermis occurs round one such 
eylinder, which lies outside the general fibrous zone. Just internal to it is a gap ie 
zone, and it would appear that this portion of the central cylinder has failed to establish 
