550 
Bancroft.—A Contribution to our 
Text-fig. 13. Part of an 
oblique longitudinal section of a 
root, showing the pitted appearance 
of the endodermis (<?.). x 400. 
(From slide K 21 n, University 
College, London.) 
In the younger examples, the endodermal cell-walls are firm 
and dark-coloured, but there is little orno black¬ 
ening of the contents (Text-fig. 14, a). In 
one or two instances the cells of the endo¬ 
dermis in the neighbourhood of the xylem 
poles remain unblackened (PI.XXVII,Fig. 3,<2), 
as if their contents had been originally less 
dense. It is possible that these cells may 
have functioned as ‘ passage cells k 1 
The cortical cells are regularly, and more 
or less concentrically, arranged in the inner¬ 
most layers; they tend to become more 
irregular, and also slightly thicker-walled, 
towards the periphery of the root. There are 
apparently no intercellular spaces. The con¬ 
tents of the cortical cells are occasionally 
preserved, presenting similar characters to 
those described in the case of the stem, though 
they are much less dense. 
In the majority of cases the outermost 
cortical layer, consisting of thick-walled dark¬ 
ened cells, forms the external covering, or 
exodermis, of the root. In one or two well- 
preserved examples, however, the outer pili¬ 
ferous layer is still present, overlying the 
Text-fig. 14. a, a portion of a very young root showing the outgrowth of an external cell as 
a root-hair, h. e., endodermis of which most of the cells have unblackened contents, x 400. (From 
slide K 21 /, University College, London.) b } a portion of a root in which the piliferous layer, p., 
and several root hairs, h ., are shown t ; ex ., exodermis, x 230. (From slide Q. 108, Cash collect.) 
1 Haberlandt, G.: Physiological Plant Anatomy. English Edition, 1914. See pp. 370 and 372. 
