CH. IV] 



XYLEM, PHLOEM. 



57 



The word xylem indicates that it is the woody part 

 of the bundle, and it will appear later that the wood of 

 trees, in the ordinary sense of the word, is in fact chiefly 



PP- 



FIG. 23. 



TRANSVERSE SECTION THROUGH THE STEM OF Helianthus tuberosus, 

 THE JERUSALEM ARTICHOKE. 



e, endodermis. 



s. t, sieve tube. 



cb, cambium. 



m. r. p, medullary ray. 



x. /, xylem fibre. 



c, cortex. 



/, pericycle-fibres. 



c. c, companion cells. 



i. cb, interfascicular cambium. 



d. v, dotted or pitted vessel. 

 p. x, spiral vessel. 



p. p, pith. 



made up of the xylem of a great number of vascular 

 bundles. 



