Fig.  /,  cross-sec tioiiof  the  stem  of  Pinus  Strobus  (two  years' growth),  showing 
the  distribution  of  tannin.  Section  drawn  as  it  appears  after  applying  solution 
of  anhydrous  ferric  chloride  in  absolute  alcohol.  The  cells  shaded  dark  are 
those  which  contain  tannin.  Magnification,  100  diameters;  a,  periderm  (cells 
mostly  containing  tannin  and  coloring  matter);  b,  tannin  cell  in  cortex;  b'}  bf/ 
other  tannin  cells; ■  c,  cambium  zone  containing  many  cells  rich  in  tannin;  d, 
medullary  ray,  showing  tannin  in  some  of  its  cells;  ring  of  growth;  s,  secre- 
tion reservoir  in  cortex;  s',  secretion  reservoir  in  xylem. 
