76 
North  American  Conifercz. 
(Am.  Jour.  Pharm. 
I   February,  1896. 
spaces,  and  still  further  outward,  next  the  pitted  pericycle  tissue, 
was  an  arc  of  thick- walled  fibres  in  one  or  two  «rows. 
The;distribution  of  tannin  in  the  leaf  was  found  to  be  similar  to 
that  already  described  in  the  leaf  of  P.  rigida. 
A  cross-section  of  a  stem  of  one  year's  growth  showed  the  fol- 
lowing structure  :  At  the  exterior  a  thick-walled,  small-celled  epi- 
dermis, supported  by  a  much  larger-celled  hypoderma,  whose  cells 
were  somewhat  lignified,  but  much  thinner-walled.  This  was  suc- 
ceeded internally  by  a  few  layers  of  stony  tissue,  abutting  on  a  layer 
Fig.  14.,  cross-section  of  leaf  of  Pinus  palustris,  magnified  65  diameters. 
Scl,f,  sclerenchyma  fibres  bounding  the  bast  on  the  outside;  ep.,  epidermis;  hy, 
hypodermal  fibers;  st,  stoma;  f  p,  folded  parenchyma  composing  mesophyll; 
en,  endodermis;  sec,  r,  secretion  reservoir;  ph,  phloem  of  one  of  the  bundles; 
trf,  t,  pitted  pericycle  or  transfusion  tissue;  xy,  xylem  of  a  bundle;  scl,  /, 
sclerenchyma  fibers  protective  to  the  xylem;  sp,  intercellular  space. 
of  phellogen.  Interior  to  the  phellogen  succeeded  a  considerable 
thickness  of  large-celled  parenchyma,  through  which  were  scattered 
stone  cells,  either  singly  or  in  clusters  of  from  two  to  eight  or  more. 
Here  also  occurred  secretion  reservoirs,  which,  in  structure  and  dis- 
tribution, did  not  differ  materially  from  those  of  the  other  species 
described.  Now  and  then,  also,  a  crystal  cell  containing  crystals  of 
calcium  oxalate,  similar  in  appearance  to  those  already  described  in 
