238 Groom.— On Dischidia raffle siana [Wall). 
suggest that the mode of development and arrangement of 
the root-hairs is partially dependent on the local distribution 
of moisture. The pitcher-roots are, for the most part, not in 
contact with the walls of the pitcher, hence the epidermis and 
root-hairs are uniformly developed round the root (except 
where the contents of the pitcher are unevenly distributed) : 
but where these roots come into contact with one another, or 
with the wall of the pitcher, there is a formation of hairs 
similar to that of the attaching-roots excepting that there are 
no long marginal hairs. Hence the latter are peculiar to the 
attaching-roots, and certainly they are admirably adapted to 
hold the root fast to the supporting surface. The hairs of 
the pitcher-roots, and the ventral hairs of the attaching-roots, 
persist and live for a long time, but they become cuticularized 
tolerably early in life. In the attaching-roots the process of 
cuticularization takes place at an earlier date, and is more 
extensive, than in the pitcher-roots. Thus the walls of these 
hairs are well cuticularized whilst the lateral walls of the 
epidermal cells to which they belong still consist of pure 
cellulose. 
Except at the region of contact, the epidermis of the root 
speedily disintegrates and the subepidermal cells form the 
external coat of the root. They form a distinct layer of cells 
with cuticularized and lignified walls, and have no intercellular 
spaces between them : in fact, they constitute a typical epider- 
moidal layer (exodermis). Two sorts of cells take part in the 
formation of this layer : first, ordinary cells, elongated in the 
direction of the long axis of the root, and possessing only 
a thin film of protoplasm lining the walls which are by no 
means thick ; secondly, smaller cells, of the same radial 
diameter as the preceding, but not elongated in the direction 
of the long axis of the root, possessing a very thick suberized 
external wall, and having a conspicuous nucleus embedded in 
a considerable mass of protoplasm. These two varieties of 
cells form longitudinal lines of cells which often regularly 
alternate in such a manner that the small cells almost look 
as if they had been cut off from the ends of the long cells. 
