AnjkiuaryP?8a96m  }  North  American  Conifer  ce.  29 
The  branches  and  younger  portions  of  the  trunk  are  smooth- 
barked,  the  wood  is  light,  soft  and  easily  worked,  being  less  resin- 
ous than  that  of  most  other  species  of  its  genus. 
MICROSCOPICAL  STRUCTURE. 
Sections  of  the  stems  of  various  ages,  of  roots  showing  two  or 
three  rings  of  growth,  and  of  the  leaves,  were  made  and  tested  in 
various  ways. 
Sections  of  twigs  of  various  ages  were  tested  for  tannic  matters, 
the  following  reagents  being  employed  011  different  sections :  Aque- 
ous solution  of  ammonio-ferric  alum,  solution  of  ammonium  molyb- 
date,  solution  of  potassium  bichromate,  solution  of  osmic  acid,  and 
solution  of  anhydrous  ferric  chloride  in  absolute  alcohol.  The  latter 
reagent  was  chiefly  relied  upon,  the  other  tests  being  used  as 
confirmatory. 
It  was  found  that  the  tannin  is  of  the  variety  that  gives  a  green 
precipitate  with  ferric  solutions,  although  the  freshly  cut  sections 
showed  a  blue-black  color,  due  to  some  accompanying  compound. 
It  pervades  the  protoplasm  (1)  in  many  cells  of  the  cambium 
zone ;  (2)  in  numerous  large,  parenchymatous  cells  of  the  bast 
layer ;  (3)  in  numerous  parenchymatous  cells  throughout  the 
cortex ;  (4)  in  the  two  or  three  circles  of  granular  cells  surround- 
ing the  resin  ducts  in  the  cortex  ;  (5)  in  many  of  the  collenchyma 
cells  beneath  the  periderm ;  (6)  in  many  cells  of  the  phellogen 
and  young  cork,  and,  accompanied  by  coloring  matters,  in  many 
of  the  mature  cells  of  the  periderm ;  (7)  it  also  occurs  in  many 
of  the  parenchyma  cells  of  the  pith;  (8)  the  younger  tracheids 
next  the  cambium  zone  contain  a  little  ;  (9)  some  of  the  medullary 
ray  cells  of  the  xylem  contain  a  little  ;  and  (10)  there  is  a  little,  also, 
in  some  of  the  secreting  cells  surrounding  the  resin  ducts  in  the 
xylem.  As  a  whole,  though,  the  xylem  tissues  contain  but  a  small 
proportion  of  tannin  as  compared  with  the  tissues  exterior  to  the 
cambium  zone.    Studies  of  older  stems  gave  like  results. 
Similar  results  were  obtained  from  the  study  of  sections  of  the 
root,  except  that  it  was  found  that  the  root  is  relatively  richer  in 
tannin.  More  was  found  in  the  medullary  rays  in  the  xylem,  and 
more  in  the  secretion  cells  about  the  resin  ducts  in  the  xylem,  than 
in  the  stem ;  but  here,  as  in  the  stem,  the  xylem  tissues  contain 
little  as  compared  with  the  bark. 
The  distribution  of  tannin  in  the  leaves  was  also  studied,  with  the 
