ANATOMY OF THE ROOTS OF PALMS. 439 
Pericycle. 
The pericycle is usually a very definite layer, but in the contractile root of Corypha 
wmbraculifera it is ill-defined. Lignification generally obtains (Pl. 49. figs. 45 & 46), 
but in Plectocomia elongata and Phenix sylvestris the walls are thin and consist of 
cellulose. In Sabal glaucescens the elements are non-lignified, but scalariformly marked. 
In Hyphene thebaica lignification is partial and in Sabal Jilamentosa general, but 
cellulose walls occur, particularly opposite the protoxylem. 
The individual elements are almost invariably several times longer than broad, as in 
Livistona oliveformis (Pl. 49. fig. 46). 
In Arenga Wightii, however, they are short and square. 
The pericycle may be one layer of cells in thickness throughout, as in Livistona 
oliviformis (Pl. 49. figs. 45 & 46), Caryota urens, and Caryota sp.; or may be irregularly 
doubled opposite the phloem in Sabal Adansonii. 
In other roots the pericycle is two-layered throughout. This occurs in Areca Catechu, 
Caryota Rumphiana, Phenix veclinata, where the lignification is greatest opposite the 
phloem-groups; Metroxylon Sagu, in which the cells of the inner layer are much reduced 
in size opposite the protoxylem ; and in Geonoma pumila, where the pericycle is com- 
pressed opposite the protoxylem and expanded opposite the phloem. 
In Cocos nucifera, Kentia sp. (Pl. 49. fig. 47), Sabal filamentosa, and Hyphene 
thebaica the pericycle is typically two-layered, but is irregularly reduced to one layer at 
any point; while in Cocos botryophora and Cocos plumosa reduction to one layer occurs 
only opposite the protoxylem, and in Latania Loddigesii opposite both xylem and 
phloem. 
In Arenga Wightii the two-layered pericycle becomes irregularly three-layered 
locally, and in Sabal glaucescens three layers occur opposite the phloem, the pericycle being 
elsewhere two-layered. | 
In Sabal Palmetto the pericycle is three-layered, and only reduced to two layers 
opposite the protoxylem. 
In Phenix sylvestris the pericycle is interrupted opposite the protoxylem and the 
external vessels abut directly on the endodermis, as De Bary (6) showed to be the case in 
grasses. 
Fibrous Zone of Sclerenchyma. 
Following the pericycle internally is a zone of fibrous tissue, generally of considerable 
radial thickness, in which lie the elements of the xylem and phloem. This normally 
presents the form of a regular circle in cross-section, e. g., Sabal Jilamentosa (Pl. 50. 
fig. 75), but may be lobed internally, as in Phenix dactylifera (Pl. 50. fig. 68), externally 
(P1. 50. fig. 88), or may be incomplete on one side, as in Dypsis madagascarensis (Pl. 50. 
fig. 63), or broken up into a number of separate strands, as m Areca sp. (Pl. 50. fig. 56). 
The elements of this zone are usually elongated lignified fibres, generally thick- 
walled and pitted. In some cases they are very densely ligni&ed and indurated, as, for 
instance, in Vartinezia caryotifolia. 
