44.2 DR. ERIC DRABBLE ON THE 
are present; in Phenix sylvestris (Pl. 50. fig. 73) there is a single irregular ring of 
them; in Zatania Commersonii (P). 50. fig. 72) the number of internal elements is greatly 
increased and they are arranged in two or three irregular rings; while in Raphia 
Hookeri (Pl. 50. fig. 71) and Corypha wmbraculifera (Pl. 50. fig. 70) they are closely 
packed and scattered throughout the whole of the fibrous zone, which here extends to 
the centre of the root, no pith being present. 
Mohl (1) observed in Diéiplothemium maritimum and Chamedorea elegans that 
two peripheral xylem-groups might converge internally and abut on a single large 
internal vessel, thus forming a V-shaped structure, between the two arms of which might 
lie a phloem-group. 
De Bary (6) described this phenomenon as follows :—‘ In thick root-bundles, some or 
all of the above xylem-plates converge in pairs in the form of a V, the groups of phloem 
lying inside a V are often smaller than those lying in between two V's. The latter are 
frequently large radially placed plates, while the former are roundish groups. This 
occurs in an exquisite form in the aerial roots of an Aroid cuitivated in Halle under the 
name of Philodendron Imbe and also in Palms. .... In Chamedorea elegans the 
irregularity goes further. In the corner of the V lies asmall roundish group of phloem. 
Between every two V's a similar group lies towards the outside, while further inside a 
second occurs which is elliptical in cross-section, and is separated from the outer group 
by interstitial sclerenchyma in which vessels frequently lie. Thus both an inner and an 
outer row of phloem-groups are present in the otberwise typical bundle." 
Simple xylem V's, between the arms of each of which lies a small phloem-group, are 
found in Kentia Forsteriana (Pl. 50. fig. 75) and Livistona australis (Pl. 50. fig. 64). 
In Raphia Hookeri (Pl. 50. fig. 71) a further complication is found, a xylem V often 
embracing between its arms not a small phloem-group but a phloem V, which again 
embraces a xylem-group. In this species what may be described as xylem Y's also 
occur, the external xylem-groups abutting in pairs internally on the outermost element 
of a radial series of two or more large vessels. 
In Heterospathe elata (Pl. 50. fig. 73) this peculiarity is still more pronounced. Two 
xylem-groups approximate internally, forming a V just incomplete at itsapex. Between 
the arms of this lies a phloem V, which in turn embraces a xylem V, and this again a 
small phloem-bundle. In this root the phloem Vis are sometimes incomplete, one limb 
being continuous with the phloem-group at the apex of the V, while the other is separated 
from it by an intervention of fibrous ground-tissue. 
In Raphia Hookeri (Pl. 50. fig. 71) the phloem-groups extend centrally to a greater 
distance than usual, and in Latania Commersonii (fig. 12), as already mentioned, phloem- 
strands are distributed throughout the fibrous zone. 
. In Phenix sylvestris (Pl. 50. fig 73) there isa greater development of xylem-vessels in 
the radial bundles than is usually found, the metaxylem consisting not of a single radial 
row of vessels, but of two or more rows. 
(— In Licuala gracilis (Pl. 50. fig. 64) internally to, and in close connection with, the 
larger elements of the metaxylem occur several smaller elements, a point of considerable 
interest, which will be dealt with below. 
