THE PLANT BODY 



47 



taxon consisting of the family Winteraceae and the genera Tetracentron 

 and Trochodendron, were described. Other vesselless genera — Sarcandra 

 in the Chloranthaceae (Fig. 23) and Aynborella (Fig. 24), perhaps con- 

 stituting a family close to the Monimiaceae — have been added to the 



Fig. 23. Transverse section of part of a two-year-old stem of Sarcandra showing 

 vesselless xylem with multiseriate and uniseriate rays in the first annual ring. B, a 

 highly magnified part of A to show detail. ( From Swamy and Bailey. ) 



vesselless group. But the group is not phylogenetically related; they 

 constitute surviving remnants of several ancestral stocks. 



Critical and extensive study of the distribution of vessels in the plant 

 body shows that in the dicotyledons vessels apparently appeared first 



