200 
North  American  Conifer  ce. 
Am.  Jour.  Pharm. 
April.  1896. 
rather  slender,  often  concave  on  the  inner  face,  deep  green,  and 
conspicuously  sheathed  at  their  base  by  sheaths  which  attain  a  length 
of  half  an  inch  or  more ;  its  cones  are  rather  persistent,  ovate,  I  y2 
to  2  inches  long,  and  with  the  thickened  scales  tipped  with  a 
minute,  weak  prickle. 
MICROSCOPIC  STRUCTURE. 
A  cross-section  of  the  leaf  showed  usually  one  convex  and  one 
concave  or  flat  side;  the  excessively  thick-walled  epidermal  cells 
Fig.  17,  cross-section  of  the  leaf  of  Pinus  echinata,  magnified  100  diame- 
ters.   St,  stoma;  hy,  hypoderma;  en,  endodermis;  sec.  r,  secretion  reservoir. 
were  of  rather  large  size,  and  strengthened  beneath  by  a  single- 
layered  hypoderma  composed  of  cells  that  were  only  moderately 
thick-walled.  The  secretion  reservoirs,  usually  two  in  number, 
were  of  large  size,  strengthened  by  a  circle  of  moderately  thick- 
walled  cells,  and  located  contiguously  to  the  hypoderma  on  the 
inner  face  of  the  leaf,  at  a  little  distance  from  the  angles. 
The  mesophyllwas  of  the  usual  folded  walled  variety.  The  endo- 
dermis had  the  exterior  wall  of  its  cells  decidedly  thickened.  The 
