578 
Structure  of  As  arum  Canadense,  L. 
km.  Jour.  Pharm 
December,  1894. 
stituting  a  cylinder-sheath,  a  structure  not  often  seen  in  the 
rhizomes  of  dicotyls. 
The  epidermis  persists  even  on  rhizomes  that  are  quite  old,  cork 
not  being  formed  beneath  it,  as  it  is  in  the  case  of  most  other  rhi- 
zomes of  dicotyls.    Attached  to  the  epidermis  are  seen  scattered, 
Fig.  4. 
simple  hairs,  each  consisting  of  several  elongated  cells  arranged  in 
linear  series.  Beneath  the  epidermis  are  several  layers  of  collen- 
chyma  cells,  which  in  transverse  section  are  usually  tangentially 
elongated.  The  cells  show  a  tendency  to  fissure  along  the  thicken- 
ings in  a  tangential  direction. 
