STRUCTURE OF THE STEM 8ST 
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. 
e Beeeg*hs9 
SHIH 
O 
4) 
eS. 
sesso” 
Fic. 55. — Diagrammatic Cross-Section of an Annual Dicotyledonous Stem. 
(Somewhat magnified.) 
Pp, pith ; fv, woody or fibro-vascular bundles; e, epidermis; 0, bundles of hard 
bast fibers of the bark. 
Fie. 56. — Diagrammatic Cross-Section of One-Year-Old Aristolochia Stem. 
(Considerably magnified.) 
e, region of epidermis; 6, hard bast; 0, 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. 
