— 240 — 



outside this is a tliin-walled endodermis whicli on its out- 

 ward side bears shreds of tlie cortex. , 



The stocliitig 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 togethet. 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 pennaia. 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 

 Ihe 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 



