I30 ANATOMY OF STEM, ROOT AND LEAF 



brancnes and stems are small brownish or whitish spots termed 

 knticels ; they are well seen on elder stems, potato tubers, and 



Fig. 6o. — Diagrams illustrating secondary growth in thickness of the stem of a dico 

 tyledon. A, A young stem before the formation of interfascicular cambium. ^, After inter- 

 fascicular cambium has formed. C, The same stem two years old. c Epidermis ; c cortex ; 

 a endodermis ; / pericycle ; iti primary wood ; r cambium ; b primary bast of a vascular 

 bun'dle ; r^ interfascicular cambium; p pith or medulla ; ?« medullary rays; n phellogen ; 

 cork; ci secondary cortex ; x^ and x^ annual rings of secondary wood; jl and s^ 

 rings of secondary bast. 



