Am.  Jour.  Pharna.  \ 
December,  1896.  J 
North  American  Conifer ce. 
645 
form  and  in  its  light,  delicate  spray,  and  is  therefore  much  cultivated 
for  ornament. 
MICROSCOPICAL  STRUCTURE. 
The  cross-section  of  a  twig  of  two  years'  growth,  Fig.  32,  showed 
at  the  outside  an  epidermis  already  mostly  displaced  by  periderm 
formations.  Beneath  the  periderm  layer  was  a  cortex  composed  of 
parenchyma  cells  of  small  or  moderate  size,  thickly  interspersed 
Fig.  54.. — Small  portion  of  longitudinal-tangential  section  of  the  inner  bark 
of  Tsuga^Canadensis,  magnified  about  75  diameters,  a,  a,  medullary  rays,  the 
cells  containing  much  starch  ;  b,  b,  stone  cells  ;  c,  row  of  cells  containing  crys- 
tals of  calcium  oxalate  ;  s,  cell  containing  oleoresinous  secretion. 
with  much  larger  ones.  The  latter  contained  either  tannin  or  muci- 
lage, or  both.  There  were  also  many  cells  containing  crystals,  and 
scattering  stone  cells,  occurring  singly  or  in  clusters  of  a  few.  The 
bast  layer  likewise  contained  numerous  tannin  cells,  and  these,  as 
viewed  in  transverse  section,  were  larger  than  the  other  cells  of  this 
layer.    Many  of  the  medullary- ray  cells  and  cells  of  the  pith  con- 
