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 pennata. 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 



