122 



PHARMACEUTICAL BOTANY 



minute and simple structure, being merely elongations of the 

 epidermis of the root back of the root cap into slender tubes with 

 thin walls. 



PIG. 57. Cross-section of rootlet in the region of the root-hairs. (From Stevens.) 



The tip of each rootlet is protected by a sheath- or scale-like cover- 

 ing known as the root cap, which not only protects the delicate grow- 

 ing point, but serves as a mechanical aid in pushing its way through 



FIG. 58. Root-hairs, with soil-particles adhering. (Gager, after Sachs.) 



the soil. The generative tissues in the region of the root cap are: 

 plerome, producing fibro- vascular tissue; periblem, producing cortex; 

 dermatogen, producing epidermis; and calyptrogen, producing the 

 root cap. 



