So 
Structure  of  Iris. 
/Am.  Jour.  Pharm. 
\    February.  1595. 
A  transverse  section  of  the  rhizome  shows  a  distinct  cylinder- 
sheath  separating  the  central  cylinder,  which  contains  numerous 
scattered  vasal-bundles,  from  the  cortex,  which  contains  relatively 
few.  The  thickness  of  the  cortex,  compared  with  the  central 
cylinder,  is  about  as  one  to  five.    The  sheath  proper  consists  of  a 
Fig.  4. 
single  row  of  tangentially  elongated  and  thickish-walled  cells,  but  is 
stengthened  interiorly  by  two  or  three  thicknesses  of  tangentially 
elongated,  somewhat  fibrous  cells. 
The  vasal-bundles  of  the  central  cylinder  are  much  more  crowded 
toward  the  exterior  of  the  cylinder  next  the  sheath,  and  are  mostly 
smaller  than  the  more  scattered  ones  toward  the  centre  of  the  stem. 
