356  Structure  of  Our  Hemlock  Barks.      { Am jX*im"m' 
(d)  Tritelia  uniflora,  of  N.  O.  Liliaceae ;  habitat,  Buenos  Ayres ; 
flowers. 
(V)  Deudrobium  heterocarpurn,  the  flowers  of  an  orchid. 
(/)  Oncidium  inosrnum,  the  flowers  of  an  orchid. 
(g)  Geonoma  pamila,  N.  O.  Palmese ;  habitat,  tropics  of  the  West- 
ern Continent.  The  violet  odor  emanates  from  the  young  green 
parts. 
(h)  Many  acacias  develop  the  odor  of  Cassie,  which  is  considered 
an  approach  to  the  violet,  as :  A.  farnesiana,  Willd.;  A.  bertoloni  j 
A.  lophantha,  A.  dealbata,  A.  pycnantha,  A.  suaveolens,  A.  odor- 
atissima,  Willd.;  A.  latronum,  Willd  ;  and  A.  lomatocarpa,  DeCan- 
dolle. 
STRUCTURE  OF  OUR  HEMLOCK  BARKS.— 
By  Edson  S.  Bastin. 
Only  five  species  of  the  genus  Tsuga  are  known  ;  two  of  these 
belong  to  Eastern  Asia,  one,  Tsuga  Canadensis,  Carriere,  is  the 
common  hemlock  spruce  of  the  Eastern  United  States ;  and  the 
other  two,  Tsuga  Mertensiana,  Carriere,  and  Tsuga  Pattoniana,  Brewer 
and  Watson,  are  natives  of  the  Pacific  Coast  of  North  America.  All 
are  trees  of  large  size  and  graceful  habit,  and  the  first  four  are  very 
closely  allied,  being  so  similar  in  appearance  that  they  are  with 
difficulty  distinguished,  while  the  fifth,  Tsuga  Pattoniana,  is  some- 
what aberrant  in  its  characters,  approaching  more  closely  the  pines 
and  spruces  in  its  structure 
Tsuga  Ca?tadensis  is  an  abundant  species  in  many  portions  of  the 
Eastern  United  States  and  Canada,  ranging  in  its  habitat  from  Nova 
Scotia  to  Delaware  on  the  east,  extending  southward  along  the 
Alleghanies  to  Alabama,  and  westward  along  the  northern  ranges 
of  States  and  the  Canadian  border  to  Minnesota.  It  is  easily  dis- 
tinguished from  the  coniferous  trees  with  which  it  is  associated,  by 
its  small  cones,  one-half  or  two-thirds  of  an  inch  long,  pendulous  at 
the  ends  of  the  branches ;  by  the  slender,  spreading  branchlets 
which  have  crowded  apparently  two-ranked  leaves  along  their  sides ; 
and  by  the  distinctly  petiolate,  flattened,  linear,  denticulate  leaves, 
which  are  green  above  and  glaucous  beneath,  and  provided  with  a 
single  resin  duct  on  their  dorsal  surface.  Its  trunk  is  extensively 
employed  for  lumber  and  its  bark  for  tanning  purposes.  Its  pitch, 
also,  which  is  extracted  from  the  old  bark  by  boiling,  is  employed 
