38i THE STRUCTURE OF ECONOMIC PLANTS 



B 



Fig. 194. A, median longisection of primary root ; B, transection of primary root 0.7 

 mm. from tip; C, schematic diagram of hypocotyl showing vascular transition from root to 

 cotyledons ; a, h, bundles which anastomose and form double bundle of cotyledon ; a' , h , 

 lateral metaxy'lem elements which form lateral bundles of cotyledons : cal, calyptrogen ; 

 w, cortex; co/, cotyledons ; J^«, dermatogen ; ^c/, epicotyl ; ««, endodermis ; ^p, epidermis; 

 hd, hypodermis ; lb, lateral bundle to cotyledon ; mh, median double bundle of cotyledon ; 

 mx, metaxylem; fbm, periblem ; pel, pericycle; pd, primary phloem duct; p, pith; pi, 

 plerome; /)x, protoxylem ; re, root cap. (After Crooks.) 



