ANATOMY OF THE ROOTS OF PALMS. 433 
Tegumentary System. 
Beneath the limiting layer usually lie several layers of elongated, lignified, and more or 
less pitted cells, followed internally by lignified fibrous elements. These together form 
the outermost cortical zone and will be referred to as the Tegumentary System. In 
such a case lignification commences in the external layers of the outer zone of square-ended 
cells and proceeds centripetally. Whilst this is going on, lignification sets in in the more 
internal fibrous zone and proceeds centrifugally. In many of the roots examined a layer 
of cellulose-walled elements intervenes between the two zones of the tegumentary system, 
which has not yet been reached either by the centripetally or the centrifugally proceeding 
lignifieation. This is well shown in Phenix sylvestris (Pl. 48. fig. 16). In other cases 
lignification may be extensive in the outer zone but absent in the internal fibrous zone, and 
here lignification proceeds centripetally only, as in Caryota ochlandra (Pl. 48. fig. 15) and 
Livistona chinensis. In Dypsis madagascarensis (Pl. 48. fig. 17) the two outer layers only 
are lignified ; these are followed by six or seven layers of square cells with dark contents, 
which resist the action of strong sulphurie acid and give all the reactions of cork. 
In Cocos nucifera the tegumentary layers are much indurated. 
In Corypha australis the outer elements are lignified, thick-walled, and pitted; the 
inner ones are square-ended and pass gradually into the internal parenchymatous 
cortex. 
In Sabal Palmetto the outer elements alone are lignified and all are parenchymatous. 
In Plectrocomia elongata the inner elements are densely lignified and their lumina are 
almost occluded, while the outer layers are much less strongly lignified. The same holds 
good for many roots of Kentia sp. In Plychosperma perbrevis the outer elements are 
fibrous and possess transverse walls, while the inner consist of extremely thick-walled 
deeply-pitted fibres. In Phenix dactylifera the tegumentary layers are non-lignified, 
but cuticularized. 
Many roots possess mucilage-cells in the tegumentary layers. These may be scattered 
through the outer zone, any cell being potentially a mucilage reservoir, as in Dictyosperma 
album and Kentia Forsteriana, or through the inner zone, as in Cyrtostachys Renda; or 
very definite mucilage-elements may be present, as in Caryota sp. (Pl. 49. fig. 42), where 
they take the form of elongated very thick-walled cells arranged in longitudinal series 
and containing raphides. 
Both outer and inner zones originate as small-celled parenchymatous tissue in the apex 
(Pl.48. figs. 13 & 14). The outer elements usually elongate and become pitted, but 
retain their square ends, while the inner elements generally become prosenchymatous. 
[m 
The Inner Cortex. 
The inner cortex, or cortex proper, viz. that region intervening between the 
tegumentary layers and the endodermis, is always composed of parenchymatous tissue, 
and is usually provided with lignified elements and large air-spaces. 
The inner cortex may be divided into three zones: an external, which is usually 
without air-spaces ; a broad middle zone, with large air-spaces ; and an internal zone, in 
