Am.  Jour.  Pharm. 
February,  1895. 
Structure  of  Iris. 
The  bundles  consist  of  that  modification  of  the  concentric  type  in 
which  the  xylem  elements  are  exterior,  and  the  phloem  tissues  cen- 
tral, and,  as  seen  in  transverse  section,  the  bundles  are  either  circu- 
lar or  somewhat  elliptical  in  outline.    The  ducts  are  of  rather  small 
Fig.  5. 
size.  Each  bundle  has  an  imperfectly  developed  sheath  of  thin- 
walled  cells,  differing  little  from  the  cells  of  the  adjacent  parenchyma 
except  in  their  smaller  size. 
Aside  from  the  xylem  elements  of  the  bundles  and  the  cylinder- 
sheath  with  its  strengthening  layer  of  fibrous  elements,  the  tissues 
