Am.  Jour.  Pharm. 
March,  1897. 
}       Frangula  and  Cascara  Barks. 
133 
there  be  added  2  c.c.  of  solution  of  potassa,  T.  S.,  Rhamnus  Californica 
will  immediately  produce  a  blood-red  color,  while  Rhamnus  Purshi- 
ana  will  produce  an  orange-red.  These  differences  in  intensity  of 
color,  thus  developed,  are  very  marked. 
The  deep  red  coloring  matter  so  abundant  in  Rhamnus  Califor- 
nica is  just  beneath  the  outer  cork  layer,  including  the  phellogen. 
It  can  be  very  plainly  seen  in  the  whole  bark  by  the  aid  of  a  simple 
lens. 
Fig.  8,  Rhamnus  Californica,  longitudinal  section.  A,  epidermis ;  b,  collen- 
chyma ;  c,  sclerenchyma  ;  d,  stone  cells  ;  e,  medullary  ray  ;  f,  bast  bundle  ; 
g,  parenchyma  ;  k,  crystals  of  calcium  oxalate. 
The  above  outline  seems  to  answer  well  the  purpose  of  distin- 
guishing between  the  three  barks  named  ;  but  to  detect  one  powder 
mixed  with  another  would,  perhaps,  be  very  difficult  even  to  one 
perfectly  familiar  with  the  drugs.  Rhamnus  Californica,  when  used 
as  an  adulterant  for  Rhamnus  Purshiana,  could  be  distinguished  by 
the  color  test  if  in  considerable  quantity;  small  amounts  could  hardly 
be  detected. 
The  following  addition  to  the  descriptions  of  the  two  official 
