ANATOMY OF THE ROOTS OF PALMS, 445 
the root which is enclosed within the cortex of the stem ; but in some cases, particularly 
in Kentia sp., Areca sp., Areca Catechu, Areca concinna, Dypsis madagascarensis, and 
Iriartia sp., the separate strands forming an incomplete central cylinder are continued 
often for a foot or more in the apical direction into the extracauline free portion of the 
root. 
The endodermis is first clearly recognizable in a root showing the condition figured in 
Pl. 51. fig. 91. Here the external surface of each of the ares is provided with a lignified 
endodermal coating, which may be followed round towards the interior for a varying 
distance, but is eventually lost in the ground-tissue of the root. Ina completely fused 
ring-like arrangement, such as that shown in PI. 51. fig. 90, the endodermis often nearly 
encircles it, but on the inner face of the ring it becomes indistinguishable from the cells 
of the ground-tissue. 
In the cylinder referred to, and other similar strands, the arrangement of the xylem 
and phloem, though distinctly radial, is not quite regular, the protoxylem-groups of the 
internally orientated bundles being either absent or abnormally orientated, aud the phloem- 
groups are often tangentially extended. In some cases, however, as in Areca Catechu, 
the endodermis forms a complete investment around one or more of the closed rings, and 
here the arrangement of xylem and phloem is radial and perfectly regular, as it is also 
in the case of Areca sp. (Pl. 50. fig. 76). 
The progressive union of the separate ares distally is well shown in the figures of 
Kentia (Pl. 51. figs. 95, 96, 97, & 98). 
In Pl. 51. fig. 95 the upper strand, a, is formed by the union of three originally 
distinct strands, the two lateral ones still possessing some of their internally orientated 
bundles, particularly the phloem-bundles; the central one has lost all trace of its 
internal bundles, except the large vessel which represents the internal metaxylem 
element of a bundle. "This strand is reduced to a wedge of fibrous tissue with only the 
external bundles of the originally radial series remaining. Such wedge-formation is 
very common and will be referred to below. In the strand 5 (Pl. 51. fig. 95) fusion of 
the arc by its internal edges has occurred and a strand of ground-parenchyma is 
enclosed. A small internally placed strand in which the xylem is reduced to a single 
central vessel surrounded by five small phloem-groups is seen in PI. 51. fig. 96 to join 
the strand 5, which is becoming incomplete internally, and in Pl. 51. fig. 97 has opened 
internally, the enclosed strand of parenchyma being thus again in communication 
internally with the ground-parenchyma. : 
In Gage the goe of geg Con formed by fusion of the strands is seen, but is va 
deeply lobed and is incomplete on the adaxial side. In such a stage as this the 
endodermis at the bottom of a depression in the fibrous ring may extend internally as a 
single plate of cells, or may be doubled (Pl. 49. fig. 48). ! 
CS SE SA a “ cortical " and “ medullary " parenchyma Een the 
gaps in the incomplete cylinder is shown in Pl. 51. fig. 100, where it obviously is quite 
i sible to distinguish between them. 
saat a DEM is illustrated in the annexed diagram. The closed cylinder of 
text-fig. 2 is not formed by the usual method of incurving and final coalescence of an 
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