STRUCTURE OF BOOTS 267 



the phellogen and the corky tissue outside of it. Draw. 

 The relation of bark to woody tissue in pine is shown in 

 Fig. 410. Cork tissue may be studied to advantage in 

 the skin of the potato. 



432. STRUCTURE OF ROOTS. At the growing point 

 the root has a cap (of small compact cells) which 

 protects the delicate tissues from injury (Fig. 395). 

 Such a protection is not found in growing points (buds) 

 of stems. In their internal structure roots differ from 



410. White pine stem in radial longitudinal section. 



Tracheids on the left with medullary rays crossing them. Next to the wood 

 is the phloem, then fundamental tissue, then the dark bark. 



stems, especially when very young. Young roots have 

 the radial type of bundles, and there is then usually 

 only one bundle in the root. The number of strands 

 of xylem radiating from the center differs with the 

 plant. In roots also there is almost uniformly present 

 a true endodermis. This layer is found just within the 

 cortex and is composed of rather thick- walled cells. How- 

 ever, many rhizomes and stems have a true endodermis. 

 To study corn roots: From the roots of Indian corn a few 

 weeks old cut thin cross-sections; stain and mount. With 

 the aid of the low power make a sketch showing the 



