ANATOMY OF THE ROOTS OF PALMS, 483 
57. ARECA sp. (from Glasgow). 
These roots were only obtainable in small detached portions, and are described below 
under the headings 4, B, and C, according to the type presented. 
A. Limiting-layer and cortex are as in the last root. The endodermis is only partially 
lignified, lignification delaying longest opposite to the protoxylem-groups. The pericycle 
is one or two cells thick. The cylinder is quite complete for at least half its 
circumference, while the other half consists of a series of separate ares, whose free edges 
are generally somewhat incurved, but in no case is the incurving very extensive. The 
fibrous zone consists of partially separated wedges in which lie the xylem, the phloem 
often lying in the parenchyma between two wedges. At the gaps there is often an insunk 
fibrous mass with a central vessel. 
The xylem of the lateral wedges of the ares shows a peculiar radial extension (text- 
fig, 21). 
In some cases a fibrous strand may run in the interior with several vessels, quite 
independently of any gap in the cylinder. Ne are of frequent occurrence, and there is 
considerable metaxylem-formation which always favours such an arrangement. It is by 
the lateral approximation of these metaxylem-groups that the V’s are formed. 
In the pith are bundles of fibres and some few air-spaces similar to those in 
the cortex. , 
B. The whole cylinder is composed of a number of small ares, the ends of each being 
strongly incurved. The fibrous wedges which contain the xylem are almost entirely 
separated by parenchyma, and the xylem-groups of the ends of the ares tend to point 
outwards as in the last case. Often between these arcs are found individual wedges 
which have not entered into arc-formation. Such wedges have externally developed 
endodermis, and may possess three or four xylem-groups accompanied by as many 
phloem-groups. Many internal fibrous strands are present with xylem and phloem, 
‘not in any way entering into the peripheral system of the cylinder. The most internally ` 
placed of such strands possess only a single vessel. | 
In this root the very great parenchymatous development is not accompanied by a 
‘corresponding development of the fibro-vascular tissue, and hence the separation of the 
fibrous arcs is much more marked than in any other root examined. Ja 
C. (Pl. 50. fig. 76.) In this root the arrangement of the fibro-vascular tissue is very 
On one side there is a large cylinder with continuous endodermis on the whole 
peculiar. gi 
SECOND SERIES.— BOTANY, VOL. VI. 
