66 
North  American  Conifer  ce. 
Am.  Jour.  Pharra. 
February,  1896. 
coarse  and  rigid.  Its  cones  are  from  i%  to  3%  inches  long,  ovate- 
conical,  frequently  in  clusters  of  two  or  three,  and  the  scales  are 
tipped  with  a  short  recurved  prickle. 
MICROSCOPICAL  STRUCTURE. 
The  leaves  in  cross-section  showed  two  flat  and  one  convex  sur- 
face, the  latter  much  wider  than  either  of  the  others,  so  that  the 
two  flat  surfaces  formed  a  very  obtuse  angle  with  each  other.  The 
epidermis  and  endodermis  were  somewhat  cutinized,  and  in  mature 
leaves  epidermis,  hypoderma,  pericycle,  endodermis  and  xylem  were 
all  more  or  less  lignified.  Hypoderma  composed  of  one  or  two 
layers  of  thick-walled  fibres  interrupted  at  frequent  intervals  on  all 
Fig.  8,  cross-section  of  leaf  of  Pinus  rigida,  magnified  65  diameters.  Scl,f, 
sclerenchyma  fibre  on  the  exterior  border  of  the  phloem  ;  en,  cell  of  the  endo- 
dermis ;  st,  stoma  ;  hy,  fibrous  tissue  of  the  hypoderma  \f,  p,  folded  parenchyma 
composing  the  mesophyll ;  sec,  r,  secretion  reservoir  ;  ph,  phloem  of  one  of 
the  bundles  ;  xy,  xylem  of  one  of  the  bundles  ;  trf,  t,  transfusion  tissue  com- 
posed of  short  tracheids  with  bordered  pits  ;  i,  sp,  intercellular  space  over 
stoma. 
sides  by  the  stomata.  Stomata  in  longitudinal  rows,  about  twenty- 
two  rows  in  all  on  each  leaf  Mesophyll  composed  of  rather  large 
cells,  and  imbedded  in  it  were  about  four  secretion  reservoirs,  one 
opposite  each  of  the  three  angles  of  the  leaf,  and  one  opposite  the 
middle  of  the  convex  surface.  About  the  reservoirs  were  a  few 
thick-walled  strengthening  cells  in  a  circle  composed  mostly  of 
