52 
Rev. T. A. Jefferies. 
In transverse section the cord root shows on the outside 
(Pig. 2) a piliferous layer (a) of medium sized, thin walled, square 
cells with no cuticle and with a length in longitudinal section of 
four to eight times their diameter. Some of these cells bear root 
hairs which are abundant, from 100 to 350 microns long, and easily 
visible on the cord roots with a pocket lens ; at the base the hairs 
have a diameter nearly equal to that of the cell. Frequently the 
cells of this layer show the presence of mycorhiza, the mycelium 
being visible in the cells and on their surface, and occasionally 
penetrating to the cells of the second row. The piliferous layer is 
supported by a layer (6), occasionally two layers, of similar cells. 
Sections frequently show at certain points a breakdown of the 
superficial cells and mycorhiza in the cells of the second layer, 
which thus replace the damaged cells of the outer layer. In Fig. 2 
the cell at a shows the beginning of this collapse, but the section is 
from a young root, as appears from the comparatively thin walled 
condition of the cortical parenchyma, hence the healthy state of the 
piliferous layer. Next we have a band of strengthening tissue ( c , 
d) composed of several rows, generally three, of narrow sclerenchy- 
matous fibres, having their walls pierced by a few fine pits and 
thickened at first with cellulose but afterwards becoming lignified. 
The outer layer (c) of this band of sclerenchyma is intermediate in 
structure : the cavities are slightly larger, and the walls thinner, 
than in the deeper layers, while the outer wall, being thickened on 
one side only, is considerably thinner. The fibres have a length of 
about 800 [x, roughly three times the length of the neighbouring 
elements. Inside this strengthening zone we have the parenchy¬ 
matous tissue of the cortex which occupies the greater part of the 
entire section and is divisible into three zones. The outer zone ( e ) 
is composed of cells irregularly arranged, of varying size and shape, 
the size tending to increase rapidly as we move inwards from the 
sclerenchyma. In the middle zone, the margin of which appears at 
f, the cells are practically circular and gradually assume an arrange¬ 
ment into radial rows. These rows, or groups of them, are 
separated by large air spaces, which provide for the aeration of the 
root in its wet habitat, are of schizogenic origin, and die out at the 
inner margin of this zone where the cells occupy the whole of the 
reduced circumference. The inner zone of the cortex shows a 
very perfect radial arrangement of the cells (see Fig. 3, S), the rows 
being closely applied one to another, and the individual cells 
becoming smaller and more rectangular as the endodermis is 
