68 
North  American  Conifer  ce. 
/Am.  Jour.  Pharm. 
\   February,  1896. 
much  thinner-walled  ones.  The  endodermis  was  rather  large-celled ; 
the  pericycle  was  many-layered  and  composed  of  discigerous  tra- 
cheids;  interior  to  these  were  two  open  collateral  bundles,  each  with 
about  four  one-  or  two-rowed  medullary  rays.  A  few  thick-walled 
fibres  occurred  at  the  outer  ends  of  the  phloem  masses,  but  they  did 
not  form  a  continuous  layer.  (See  Fig.  8.)  The  oleoresin  of  the  leaf 
seemed  to  be  nearly  confined  to  the  secretion  reservoirs  and  the 
secreting  cells  immediately  surrounding  them. 
Fig.  io,  starch  from  root  of  Pinus  rigida,  magnified  1,200  diameters.  The 
granule  marked  with  a  cross  shows  the  effect  of  polarized  light.  The  grain 
has  few  and  very  faint  markings,  even  the  hilum  being  in  many  instances 
difficult  to  recognize  except  by  the  aid  of  polarized  light. 
Most  of  the  mesophyll  cells  contained  some  tannin  and  a  con- 
siderable proportion  of  them  were  very  rich  in  it.  It  also  occurred  in 
the  phloem  tissues  of  the  bundles,  but  only  to  a  slight  extent  else- 
where in  the  leaf. 
A  cross-section  of  a  twig  two  or  three  years  old  showed  the  fol- 
lowing structure  : 
