68 



ROOTS 



the growing tip. This is evidently an adaptation which protects the 

 young and actively growing cells just under the root cap. In the 

 body of the root a central cylinder of wood can easily be distin- 

 guished from the surrounding cortex. In a longitudinal section 

 a series of tubelike structures may be found within the central 

 cylinder. These structures are made up of cells which have grown 

 together end to end, the long axis of the cells running the length of 



Central 

 cylinder 

 Food passes 

 down here 



Walerpdsses 

 up here 



■Epidermis 

 Corf-ex 



Root cap 



Diagram of section of a root tip, 

 showing structure. 



^ood/ bundle 



Diagram of a root tip, showing 

 root hairs, greatly magnified. 



the main root. In their development these cells have grown to- 

 gether in such a manner as to lose their small connecting ends, and 

 now form continuous hollow tubes with rather strong walls. Other 

 cells have developed greatly thickened walls, which give mechani- 

 cal support to the tubelike cells. Collections of such tubes and 

 supporting woody cells together make up what are known as 

 fihrovas' cular bundles in the wood. 



Root hairs. — Careful examination of the root of one of the 

 seedlings of mustard, radish, or barley grown in a pocket germi- 

 nator shows a covering of tiny fuzzy structures, at most 3 to 4 



