— 240 — 
outside this is a thin-walled endodermis which on its out- 
ward side bears shreds of the cortex. 
The stocking itself was originally formed by mucilage 
secreted by the young root; later on the root-hairs penetrate 
the sand (R. Price), and long after they are dead, they 
keep the sand-grains bound together. Root-hairs are found 
on the epidermis which is still entire and forms the inner 
wall of the sand-tube. The internal diameter of the stocking 
Fig. 64. Aristida pennala. A, Part of leaf in transverse 
section, slightly diagrammatic. Sclerenchyma black, 
green tissue shaded. B, Detail of A. N, Veins; C, 
Epidermis of the lower face with hairs. A, X 53; 
B and C, X 203). 
thus indicates the original thickness of the root, but from 
the disappearance of the primary cortex the root becomes so 
thin that is lies loosely in the tube. 
The straw or haulm is solid and the vascular bundles 
lie scattered in a somewhat thick-celled tissue; each of them 
U 
