ANATOMY OF THE ROOTS OF PALMS. 469 
sclerenchymatous zone enclosing a parenchymatous pith. The xylem- and phloem-groups 
lie peripherally in this zone, and there is only one irregular ring of large internal vessels. 
V-formation occurs, as there are fewer of the large vessels than there are protoxylem- 
groups. In the central pith run three sclerenchymatous strands each enclosing a large 
vessel. 
(383) AnENGA Wien, Griff. 
The limiting-layer is persistent, and consists of thin-walled slightly lignified isodiametrie 
cells and is succeeded by a zone of small, square-ended, elongated, lignified, thick-walled 
elements. The inner cortex is parenchymatous with very irregular air-spaces and strands 
of fibres bounded by stegmata. In addition to the fibres, individual thick-walled, pitted, 
lignified, parenchymatous cells occur, particularly well developed immediately around the 
endodermis, in which region air-spaces and fibrous bundles are wanting. The endodermis 
is thick-walled and lignified; the pericyele is two or three cells in thickness, and the 
elements are short and isodiametric. The xylem and phloem are embedded in a 
sclerenchymatous zone in which the vascular elements do not extend far centripetally. 
There is one ring of larger internal vessels, and centrally there is a parenchymatous pith 
with some lignified elements. 
(34) IRIARTIA sp. 
The limiting-layer cells are slightly lignified and project as papillæ on the surface. A 
. layer of thickened lignified elements with narrow lumina succeeds the limiting-layer, 
and is followed by a zone of prosenchyma, of which the outer layers are lignified. The 
parenchymatous inner cortex is traversed by bundles of fibrous elements, only the outer 
members of which are lignified. In the centre of each bundle runs a long element with 
transverse walls very like those of the sieve-tubes, but no definite pitting could be made 
out. Of these De Bary says, perhaps sieve-tubes.” Unfortunately older roots could 
not be obtained, and it was found impossible to settle the question from the available 
material. In the most internal part of the cortex run definite rounded air-spaces, and in 
this region also occur individual lightly lignified parenchymatous elements. In a root 
1 inch in diameter a complete endodermis of lignified cells exists. At one point it was 
doubled, two cells occurring on the same radius. The central cylinder in this root is 
elliptical in outline. The pericycle is two cells in thickness, except just opposite the 
protoxylem-groups, where it is reduced to one cell in thickness, The xylem and phloem 
are embedded in a prosenchymatous zone, only the periphery of which is lignified. The 
protoxylem-elements, which are only very slightly lignified, are embedded in patches of 
non-lignified tissue. V-formation is rare, but there is a tendency to xylem V's at the 
ends of the ellipse. Only one ring of internal vessels exists; these are non-lignified, but 
are embedded in lignified sheaths. Centrally there is a parenchymatous pith with very 
irregular air-spaces. 
fra seats section of a larger root the endodermis, instead of forming a complete 
ring, forms a series of ares of small radius as compared with the radius of the whole 
central cylinder. This gives a lobed outline to the cylinder, and in the depressions 
between the lobes the endodermis cannot be recognized as a definite 2 zs ground- 
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