150 



MEDULLOSEAE 



[CH. 



Fig. 439. Sutcliffia insignia Scott. A, B, E, forma u,. (After Scott.) C, D» 

 forma §. (After de Fraine.) 



A. Transverse section of stem ; a,, b, double rows of leaf -trace bundles. 



The larger black masses are the meristeles ; the smaller patches 

 represent bundles derived from the meristeles. 



B. Longitudinal section of a radially symmetrical bundle from a 



leaf-base. 



C. The junction between the primary and secondary xylem. 



D. Vascular system in transverse section : m, m', meristeles ; a, main 



stele; e, extra-fasoicular strands; It, leaf -traces; c, secondary 

 cortex. 



E. Vascular bundle from petiole showing a ring of large sieve-tubes 



surrounding the xylem, and portions of stereome strands. 



