Am.  Jour.  Pharm 
May,  1896. 
}    How  to  Distinguish  Viburnum  Barks. 
227 
guish  between  the  V.  opulus  and  the  V.  prunifolium  in  the  powder 
by  the  presence  or  absence,  in  the  powder,  of  stone-cells.  A  further 
report  on  this  point  was  promised  when  some  experience  had  been 
obtained  in  working  with  the  powders.    It  is  intended,  therefore, 
Fig.  4. — Viburnum  prunifoliuin.    Bark  of  root. 
Cross-section. 
in  this  paper  to  discuss  this  question,  and,  to  connect  it  with  the 
last  paper,  I  should  say  that  the  third  problem  above  mentioned 
will  be  considered :  What  are  the  differential  characteristics  which 
will  distinguish  the  powdered  barks  under  the  microscope  ? 
I  should  state  here,  to  those  who  have  offered  to  share  wittf  me 
