i3° 



BOTANICAL GAZETTE 



FEBRUARY 



the central axis divide in either of two planes (fig. 13). The first 

 xylem elements, having the usual spiral thickenings of the pro- 

 toxylem, become differentiated in the cotyledons; there are 4 

 groups of protoxylem, with 2-4 strands in each group, extending 





Fig. 1. — Transverse section of a branch showing epidermis, cork cambium, 

 cortex with resin ducts, phloem, xylem, pith, and a leaf trace. 



from near the tip of the cotyledon to the base of the cotyledonary 

 tube. The protoxylem is endarch (figs. 16-20). It is significant 

 that at this time there is no xylem present in the primary root or 

 in the leaf bud (stem tip). 



