94 



BOTANY: PRINCIPLES AND PROBLEMS 



The Internal Structure of the Stem. — In the cross section of a 

 typical young stem (Figs. 48, 53 and 54) there may be distin- 

 guished the same three types of tissue which are present in the 



Fig. 45. — Rootstock of Iris. 



Fig. 46. — Tuber of the potato, fehowmj; point of ittithrneiit to the parent 

 plant (at extreme light) and numerous budb or eje&,' eacli in tht axil of a 

 reduced and scale-like leaf. 



root, but they are arranged somewhat differently. Outside 

 the whole is the epidermis, consisting of a single cell-layer, and 

 often replaced entirely, at an early stage, by a zone of corky bark. 



