ADe*e^mb'e^894n■}   Structure  of  As  arum  Canadense,  L. 
S77 
circle.  The  phloem  portions  of  the  bundles  contain  no  fibrous  ele- 
ments, and  the  xylem  portions  usually  no  lignified  ones  except  the 
tracheary  tissues,  which  consist  mostly  of  spiral  and  scalariform 
Fig.  3. 
ducts  and  tracheids  of  small  or  moderate  calibre.  The  circle  of 
bundles  is  bounded  exteriorly  by  a  zone  of  parenchymatous  cells 
considerably  smaller  than  those  of  the  cortex  exterior  to  them,  con- 
