3i6 
Structure  of  Sassafras. 
(  Am.  Jour.  Phaim. 
I      June.  1895. 
Oil  cells  are  not  confined  to^this  layer,  but  occur,  though  some- 
what less  abundantly,  among  the  sieve  and  companion  cells  of  the 
inner  layer  of  the  bark.  Parenchyma  cells,  rich  in  tannic  matters, 
are  also  freely  scattered  through  the  middle  and  inner  layers. 
The  medullary  rays,  whose  course  in  the  bark  is  usually  some- 
a 
b 
c 
Fig.  4- 
what  wavy,  are  composed  sometimes  of  one,  sometimes  of  two,  and 
more  rarely  of  three  rows  of  cells. 
No  primary  bast  fibres  are  formed  in  the  root  bark,  and  the  bark 
of  roots  not  more  than  two  or  three  years  old  is  usually  destitute 
of  bast  fibres  of  any  kind. 
