Am.  Jour.  Pharm. 
September,  1895. 
Structure  of  Oiir  Cherry  Barks. 
439 
(2)  They  all  resemble  one  another  in  the  facility  with  which  the 
periderm  layers  are  separated  transversely  into  thin  sheets. 
(3)  The  medullary  rays  in  all  the  species  are  several  rows  of 
cells  thick,  though  the  number  of  cells  differs  somewhat  in  different 
species. 
(4)  In  all  the  barks  examined  the  medullary  rays  are  more  or  less 
wavy  in  their  course,  though  less  so  in  some  species  than  in  others. 
(5)  All  the  barks  show  a  strong  tendency  to  fissure  between  the 
medullary  rays  and  adjacent  bast  tissues. 
(6)  All  of  the  barks,  especially  of  the  trunk  and  older  branches, 
are  rich  in  oxalate  of  calcium  crystals,  some  of  them  containing  it 
in  such  quantities  as  to  make  sectioning  difficult. 
(7)  All  of  the  barks  possess  a  bitter,  astringent  and  more  or  less 
aromatic  taste,  but  the  bitterness  is  much  less  marked  in  some  than 
in  others,  and  the  aromatic  quality  is  very  decided  in  some,  but 
barely  perceptible  in  others. 
The  most  prominent  structural  differences  are  in  the  number, 
arrangement  and  character  of  the  sclerenchymatous  elements. 
These  and  other  differences  will  be  noticed  in  the  descriptions  of  the 
barks  of  the  different  species. 
Bark  of  the  Stem  of  Prunus  serotina. — The  periderm  or  corky  layer 
separates  readily  in  transverse  bands  from  the  rather  thin  layer  or 
cortex  beneath.  The  latter  contains  numerous  clusters  of  short 
sclerenchymatous  cells  or  stone  cells,  which  form  an  interrupted 
zone  in  this  layer  of  bark.  Just  underneath  this  layer  the  medullary 
rays,  whose  course  from  the  cambium  zone  outward  is  more  or  less 
wavy,  terminate  very  obliquely.  The  rays  in  their  thickest  part  are 
from  four  to  six  cells  broad,  and  between  them  lie  the  bast  masses 
which,  except  near  the  cambium  zone,  consist  of  crumpled  sieve 
O 
Fig.  4. — Starch  from  stem  bark  of  Prunus  serotina. 
