STRUCTURE OF HERBACEOUS DICOTYLEDONOUS STEMS 193 



B 



FIG. 172. Diagrams of highly magnified sections of an Alfalfa stem. 

 A, both cross sectional and lengthwise views of the tissues near the tip of 

 the stem, a, epidermis; I, collenchyma; e, chlorenchyma of the cortex; s, 

 starch sheath; i, pericycle; b, bast fibers; Z, conductive portion of the phloem 

 containing the sieve tubes and companion cells; c, cambium; x, xylem; and 

 p, pith; v, vascular bundle. B, section farther from the tip, showing cambium 

 ring and the closing together of the bundles. Lettering as above. 



