AfcS^S2L}   Structure  of  Asarum  Canadense,  L.  579 
In  the  thick  cortical  parenchyma  and  in  the  pith  occur  scattered 
oil-cells,  easily  identifiable  in  the  sections  after  treating  them  with 
solution  of  alcannin.  Unless  stained,  they  differ  little  in  appear- 
ance from  ordinary  parenchyma  cells,  save  in  the  absence  of  starch. 
In  the  ordinary  parenchyma  both  of  the  pith  and  the  cortex 
starch  is  abundant,  though  fine-grained.  The  grains  are  sometimes 
simple,  but  more  commonly  double,  triple,  or  in  masses  of  from 
three  to  twelve  grains.  The  hilum,  which  is  sub-central,  is  incon- 
spicuous and  seldom  fissured,  and  the  grains  show  no  distinct 
stratification  curves. 
Ihe  roots,  which  attain  about  a  millimetre  in  diameter,  have  a 
thick  cortical  parenchyma,  consisting  mainly  of  starch-bearing 
cells,  among  which,  however,  are  sprinkled  a  few  oil  cells.  The 
central  radial  bundle,  which  commonly  has  a  diameter  slightly  less. 
