THE STEM 207 
Corx.—Cork or phellem is all that tissue produced by the cork 
cambium on its outer face. Its walls become impregnated with 
a waterproof substance of a waxy character called suberin. 
og, KE) 
“ 
CO . SE 
eves S:85e ee 
f eornsh 
Fic. 137.—Part of a cross-section through branch of Cytisus laburnum. (The 
branch was cut from the tree at the end of October.) From A to £ the last annual 
ring of wood; from A to B the spring growth with large tracheal tubes (7, 7, 7); 
between B and C and D and D are wood-fibers; between C and D and D and £, 
wood parenchyma; from E to F, cambium; F to G, phloem portion; G to H, cortical 
parenchyma; M, medullary ray. Below A the last wood-fibers and wood paren- 
chyma formed the previous year. (From Sayre after Haberlandt.) 
PERIDERM.—Periderm is a name applied to all the tissue 
produced by the cork cambium (Phellogen) externally and inter- 
