390 
Vib urn  u  m  Pru n  ifo I iu  in . 
Am.  Jour.  Pharm. 
August,  1895. 
the  periderm  are  numerous  irregular  clusters  of  stone  cells.  These 
are  succeeded  in  the  inner  or  bast  layer  by  large  clusters  of  bast 
fibres  associated  with  a  few  stone  cells.  These  clusters  are  arranged 
in  bands  parallel  to  the  surface  of  the  bark,  and  are  separated  from 
each  other  radially  by  narrow,  one  or  two-rowed,  straight  medullary 
FIG.  I. 
Viburnum  opulus — Bark  of  stem. 
Cross-section. 
FIG.  2. 
o9} 
'1M 
Viburnum  opulus. 
Bark  of  trunk. 
Longitudinal  section. 
fig.  3. 
OQ«~ 
DDRn 
Viburnum  prunifolium. 
Bark  of  trunk. 
Longitudinal  section. 
rays.  The  clusters  are  also  partly  or  wholly  encased  in  thin-walled 
crystal  cells,  each  usually  containing  a  single  crystal  of  calcium 
oxalate.  These  interrupted  bands  of  bast  fibres  and  stone  cells  are 
separated  from  each  other  by  rather  broader  bands  of  soft  bast,  in 
which  also  a  few  scattered  stone  cells  and  bast  fibers  occur. 
