STRUCTURE OF THE STEM 



87 



the first season's growth. 1 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. 



FIG. 55. Diagrammatic Cross-Section of an Annual Dicotyledonous Stem. 

 (Somewhat magnified.) 



p, pith ; fv, woody or fibro-vascular bundles ; e, epidermis ; b, bundles of 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 ; o, 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. 



