448 
Structure  of  Our  Cherry  Barks.  { 
abundant.  It  was  also  very  fine  grained ;  the  grains  were  often 
rounded  and  simple,  but  also  frequently  double  or  triple.  The 
faintly  distinguishable  hilum  is  nearly  central.  The  taste  of  this 
bark  is  decidedly  bitter  and  astringent,  but  the  aromatic  or  bitter 
almond  odor  and  taste  are  usually  scarcely  perceptible. 
The  Stem  Bark  of  Prunus  Pennsylvanica. — This  tree,  when  not  in 
fruit  or  flower,  might  be  mistaken  for  a  small  specimen  of  P.  sero- 
tina,  for  the  habit  is  similar,  and  the  bark  of  the  trunk,  though 
usually  lighter  colored  and  smoother  than  that  of  the  official  species, 
is  occasionally,  in  the  old  specimens,  quite  dark  and  rough  enough 
to  resemble  that  of  young  and  thrifty  specimens  of  P.  serotina  of 
similar  size.    The  lenticels  on  the  twigs,  however,  perceptible  also 
even  on  the  older  trunks,  are  much  less  numerous.  Of  course, 
there  would  be  no  difficulty  in  distinguishing  this  species  when  in 
flower,  for  its  flowers  occur  in  umbel-like  clusters  instead  of  racemes ; 
in  early  instead  of  late  spring  ;  and  from  separate,  lateral  scaly  buds 
instead  of  on  the  ends  of  lateral  leafy  branches.  The  fruits  also 
are  red,  on  long  pedicels,  and  with  a  thinner,  more  acid  and  not  a 
bitter  taste. 
The  lenticels  on  the  trunk  are  not  so  large  as  those  of  P.  Avium, 
seldom  attaining  a  length  transversely  of  more  than  half  an  inch. 
The  corky  layer,  however,  separates  from  the  sub- lying  green  tissue 
in  a  very  similar  manner,  and  in  cross-section  this  layer  shows  a 
similar,  though  finer,  stratification.    When  the  brown  or  blackish 
Fig.  13. — Starch  from  stem  bark  of  Prunus  Pennsylvanica. 
