STRUCXUKE OF THE STEM 



87 



the first season's growth.^ Sketch the whole section without much 

 detail, and then make a detailed drawing of a sector running from 

 center to circumference and just wide enough to include one of the 

 large bundles. Label these drawings in general like Figs. 55, 56. 



-fv 



Fig. 55. — Diagrammatic Cross-Section of an Annual Dicotyledonoiis Stem. 

 (Somewhat magnlfled.) 



Pi pith ; /v, woody or flbro-vascular bundles ; e, epidermis ; 6, bundles o( hard 

 bast fibers of the bark. 



Fig. 56. 



-Diagrammatic Cross-Section of One- Year-Old Aristolochia Stem. 

 (Considerably magnified.) 



e, region of epidermis ; 6, hard bast ; w, outer or bark part of a bundle (the 

 cellular portion under the letter) ; w, inner or woody part of bundle ; c, cam- 

 bium layer ; p, region of pith ; m, a medullary ray. 



The space between the hard bast and the bundles is occupied by thin-walled, 

 somewhat cubical cells of the bark. 



1 Clematis virginiana is simpler in structure than some of the other woody 

 species. Aristolochia sections will do very well. 



