Am.  Jour.  Pharni.  \ 
August,  1896.  J 
North  American  Conifer ce. 
413 
walled  fibres.  The  layer  of  transfusion  tissue  was  moderately  thick, 
the  endodermis  large-celled,  and  the  radial  walls  of  its  cells  were 
thickened.  The  secretion  reservoirs,  which  were  located  at  the 
lateral  angles,  were  of  moderate  size. 
CHEMICAL  COMPOSITION. 
Owing  to  the  similarity  in  most  particulars  of  the  white  and  the 
black  spruces,  and  the  absence  of  sufficient  material  at  a  convenient 
time,  a  detailed  chemical  study  was  not  made  of  the  latter.  A  sam- 
ple of  bark  from  a  branch,  collected  in  the  Adirondack  Mountains, 
New  York,  in  August,  1 895 ,  yielded  the  following  percentage  results : 
Moisture  9*95 
Ash  in  absolutely  dry  bark    .  ■  2*72 
Tannin  in  "  "     "   12*13 
The  fact  that  this  sample  was  from  a  branch,  and  collected  late  in 
the  summer,  would  account  for  the  lower  percentage  of  tannin  than 
that  yielded  by  the  white  spruce. 
There  is  another  constituent  of  considerable  importance  in  the 
black  spruce,  although  it  has  not  been  studied  by  us,  and  that  is  the 
resinous  exudation,  popularly  known  as  spruce  gum.  In  1886 
Menges1  contributed  an  article  of  considerable  interest  on  this  sub- 
ject. He  showed  that  it  is  obtained  from  the  black  spruce, 
although  small  quantities  are  yielded  by  the  white  spruce.  None, 
however,  is  obtained  from  the  hemlock  spruce,  Tsuga  Canadensis,  as 
is  frequently  reported. 
The  spruce  gum  is  not  obtained  by  hacking  or  puncturing  the 
trees,  but  exudes  spontaneously  from  decayed  knots,  or  seams 
caused  by  extremes  of  heat  and  cold.  Simply  bruising  the  bark 
will  not  cause  a  flow  of  the  resin,  but  the  cavity  must  extend 
through  the  bark  and  sapwood. 
The  so-called  gum  is  collected  during  the  winter  season  by  men 
on  snow-shoes,  who  are  provided  with  a  small  tin  cup  attached  to  a 
chisel  and  long  pole,  so  that,  as  the  mass  of  resin  is  cut  off,  it  drops 
into  the  cup. 
The  largest  quantities  are  collected  in  Maine,  New  Hampshire, 
Vermont  and  Canada. 
Examination  of  the  So-called  Spruce  Gum.  Adolph  F.  Menges.  Contrib. 
Dep.  Phar.,  University  of  Wisconsin,  1886,  p.  30,  and  Amer.  Jour.  Phar., 
1886,  p.  394. 
