334 
S. Reginald Price . 
then an inner cortex of regularly arranged cells with large inter¬ 
cellular spaces (Fig. 3). 
Just above the position in which the gland cells disappear as 
such, the tissues of the root reach their full development. A 
transverse section cut in this region or a little further back, say an 
inch (24 mm.) from the root-tip, shows a typical Monocotyledonous 
root structure (Text-fig. 1). The outer layer of the cortex—the 
piliferous layer—is composed of rather small cells which appear 
rounded in transverse section. Within this there are one or two 
layers of rounded cells with no very regular arrangement, forming 
the exodermis, and this passes over into the inner cortex. The 
cells here are arranged in a very regular manner in concentric layers 
and radiating rows, with well-marked intercellular spaces between 
the corners of the cells, the whole appearing almost diagrammatic 
in arrangement, as is often the case in Monocotyledonous roots. 1 
As usual in such roots the endodermis is well marked. The stele 
is rather remarkable for a peripheral zone of sclerenchyma, several 
cells in width and representing the pericycle. On the inner edge 
of this pericyclic zone are a number of bays, in each of which is a 
small phloem group. The root is polyarch, with as many as forty 
protoxylem groups in some cases. The rest of the conjunctive 
tissue is of a distinctly sclerenchymatous type, though not so thick- 
walled as the tissue of the pericycle. In the fully mature stele 
especially there is a well marked central pith, also sclerenchymatous. 
It is this large development of sclerenchyma which gives the stele 
its great mechanical strength 
Passing to the region where the full thickness is first attained, 
say —2 inches from the tip, the general structure is practically 
the same, but now the piliferous layer justifies its claim to the 
name. Numerous root-hairs of the usual type occur, that is they 
are simply outgrowths of the outer cortical cells. On the whole 
the hairs appear less numerous than in the “ root-hair region ” of a 
typical young root, but this must he more than compensated for 
by the very great length of root surface occupied by hairs. Text- 
figure 2 shows a portion of the outer cortex of the root in this 
region. 
In the region towards the point of insertion on the stock, the 
root-hairs increase very much in length. Only herbarium material 
was obtainable of this region, but this when soaked in alcohol and 
teased out in glycerine, showed the hairs quite well. Fig. 6 is 
r cf. Bonnier and du Sablon, l.c., Fig. 512. 
