STRUCTURE OF HERBACEOUS DICOTYLEDONOUS STEMS 193 



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; Z, collenchyma; e, chlorenchyma of the cortex; s, 

 starch sheath; i, pericycle; 6, bast fibers; t, 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. 



