ANATOMY OF ENHALUS ACOROIDES. 363 
Tuar Roor. 
The most accurate description of the root has been given by Svedelius. He shortly 
describes it as a normal root-structure, and gives the following details :—The epidermis 
has very few root-hairs, functions only at a very early stage, and is separated from the 
outermost layers of the cortex by an exodermis. The other cells of the cortex are arranged 
in radial layers with intercellular spaces. In the external part large air-chambers 
separated by radial rows of tissue arise. The central cylinder occupies but a small part 
of the whole scheme of the root, and is surrounded by a slightly developed thin-walled 
endodermis. The xylem consists of very few unlignified feebly developed vessels; the 
phloem is relatively better developed. Tannin-cells are present, except inside the 
endodermis. 
The following account is more detailed and records several interesting facts not 
observed by Svedelius :— 
The root of Enhalus shows the typical structure of a monocotyledonous aquatic plant. 
The epidermis only persists as a many-layered root-cap. On the outside of the root 
there is a crushed layer of cells of hardly distinguishable structure (Pl. 36. fig. 15). 
The cortex surrounding the small central vascular cylinder is differentiated into three 
zones, the outer, middle, and inner respectively. The outer cortex consists of six layers of 
cells, of which the outer two form a thin-walled exodermis with no apparent intercellular 
spaces. "These cells are radially elongated and have darker-coloured walls as compared 
with those radially on either side. The four inner layers of this zone have thicker walls 
than the exodermis and small intercellular spaces. This zone contains pigment-cells. 
The middle and the inner cortex resemble each other when young, except thas the 
inner cortex possesses pigment-cells. They consist of thin-walled cells in radial and 
concentric rows. It follows from this arrangement that square intercellular spaces, also 
presenting a radial concentric appearance, are formed at the corners between each 
four cells and are larger towards the outside, here equalling the cells in size. As the 
root gets older the middle and the inner cortex become differentiated, the middle being a 
wide band (2} times the width of the outer cortex) becomes composed largely of 
aeriferous tissue. First, the outer layers split in the intercellular space-lines, yep 
large radial lacune of irregular size and shape. Later on, the radial walls of gs : e 
Cells in this zone collapse together, thus (Pl. 36. fig. 15) farming mee ya 2 
Spaces separated by long double rows of radial cell-walls. After ARE ^d 
meristem the middle and the inner cortex-cells become elongated dept f p 
crossed by diaphragms aft irregular intervals. The latter consist of e e D "d 
cells which are in contact with one another, and which remain Mac ls z 4 ited 
other cortical cells elongate. They appear spirally arranged, but the spirals are limi ; 
in length d for a short way round the cortex im any series o 
gth and can only be trace 
transverse sections. 
he endodermis-cells are radially the innermos 
Which remain radially arranged throughout the life of th um 
from the latter by the presence of the characteristic mus dg ond peste 
e root-bundle is exarch and usually hexarch, though it is A 
SECOND SERIES.— BOTANY, VOL. VII. 
t layer of the inner cortex, the cells of 
fe of the plant, and can be distinguished 
