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ANATOMY OF THE ROOTS OF PALMS. 471 
of the larger depression it is discontinuous as a specially differentiated layer, the cortical 
and medullary parenchyma being quite continuous. At these points the sclerenchy- 
matous ring is incomplete, and the adjacent ends are inflected, carrying inwards with 
them the last two or three xylem- and phloem-groups. The pith is parenchymatous, and 
there are many sclerenchymatous strands with central vessels. 
(86) Gronoma SzEMANNI, H. Wendl. 
The limiting-layer is of the usual type, and is followed internally by a zone of elongated 
elements densely lignified in the external layers, but becoming less and less densely 
lignified centripetally, the innermost layer of the zone being entirely non-lignified. 
Passing further in a central direction lignification gradually increases, but not to the 
same extent as in the outer layers just mentioned. The parenchymatous inner cortex 
contains air-spaces and bundles of fibres. Immediately around the endodermis are 
several isolated lignified elements, somewhat elongated, thick-walled, and pitted. The 
endodermis is of the usual lignified type. The pericycle is two cells in thickness. In a 
sclerenchymatous zone lie the xylem and phloem. Only one ring of large internal vessels 
is present. In other roots the outer portion of the ground-tissue of the central cylinder 
is non-lignified, and the phloem- and protoxylem-groups are embedded in parenchyma. 
(37) Geonoma PUMILA, H. Wendl. 
The limiting-layer is almost entirely exfoliated, the periphery being then occupied by 
an external cortex of the usual type of elongated cells, passing gradually into the 
parenchymatous inner cortex, which is provided with comparatively large and irregular 
air-spaces. In this region lie long, square-ended, lignified elements. The endodermis is 
of the usual lignified type. The pericycle is two layers in thickness; its elements are 
parenchymatous, much compressed opposite the protoxylem, but expanding opposite the 
phloem. The zone in which the phloem and protoxylem are embedded is parenchymatous 
and non-lignified, but internally there is a zone of lignified elements in which lies one 
ring of large internal vessels. There is centrally a loose parenchymatous cortex with 
irregular air-spaces. 
(38) CHRYSALIDOCARPUS LUTESCENS, H. Wendl. 
The limiting and tegumentary layers are developed as usual, and are followed by the 
outer dense zone of the parenchymatous inner cortex, in which are many elements 
containing dark-coloured mucilage. The inner zone shows small well-developed air- 
spaces arranged roughly in three circles. Ia this region are also bundles of fibres very 
richly developed, especially in the innermost layers. The endodermis is lignified and the 
pericycle is one-layered. The sclerenchymatous zone encloses a large central pith. In 
the sclerenchyma lie the xylem and phloem. There is only one ring of internal vessels, 
and these can usually be allotted to their particular protoxylem-groups, but occasionally 
V-formation obtains. The pith contains many small definite air-spaces. 
In a section of a large root taken some distance from the stem-base, the central cylinder 
exhibits a depression on one side, and into this the endodermis dips. In this region the 
