Am.  Jour.  Pharrn. 
July,  1S96. 
North  American  Coniferce. 
333 
The  herbarium  should  be  preserved  in  a  suitable  receptacle,  free 
from  dust.  This  may  consist  of  a  cabinet,  with  shelves  of  the 
proper  width  and  depth  for  the  genus  covers  to  slide  in  easily,  or  of 
a  number  of  plain  boxes  with  shelves  4  or  6  inches  apart  and 
doors  which  shut  flush.  The  names  of  the  orders  can  be  pasted 
upon  the  shelves  or  affixed  to  the  edge  of  the  genus  board,  which 
contains  a  list  of  the  genera  of  the  order,  and  is  inserted  at  its 
beginning. 
A  CONTRIBUTION  TO  THE  KNOWLEDGE  OF  SOME 
NORTH  AMERICAN  CONIFERS.  ^ 
By  Edson  S.  Bastin  and  Henry  Trimble. 
(Continued  from  page  337.) 
THE  GENERAL  CHARACTERS  OF  THE  SPRUCES. 
The  important  genus  Picea  numbers  about  a  dozen  species,  all 
inhabiting  the  mountainous  regions  of  the  North.  Two  of  them  are 
native  to  the  Northeastern  United  States,  three  to  our  Northwest, 
two  are  European  and  five  are  Asiatic.  They  are  straight-boled, 
evergreen  trees,  of  pyramidal  form  and  rather  slow  growth ;  whitish, 
soft,  close-grained  and  somewhat  resinous  wood  ;  alternate,  acicular, 
tetragonal  leaves,  which  are  very  numerous  and  compactly  arranged 
on  the  younger  branches,  and  seldom  exceed  an  inch  in  length. 
The  leaves  are  sessile  and  the  persistent  bases  prominent,  giving 
a  rough  appearance  to  the  branches.  The  tetragonal  form  of  the 
leaf  is  due  to  the  fact  that  both  the  upper  and  the  lower  surfaces  are 
keeled.  Stomata  usually  occur  in  rows  on  all  four  faces ;  but,  fre- 
quently, the  rows  are  less  numerous  on  the  two  faces  of  the  lower 
surface.  Internally,  the  leaves  show  a  central  stele,  containing  a 
small,  usually  distinctly  double,  collateral  fibro-vascular  bundle,  sur- 
rounded by  a  more  or  less  copious  transfusion  tissue,  similar  to  that 
of  the  pines.  The  stele  is  separated  from  the  mesophyll  by  a  dis- 
tinct endodermis.  The  mesophyll  is  composed  of  parenchyma, 
which  has  wavy,  but  not  folded,  walls.  The  epidermis  is  supported 
by  a  hypoderma,  usually  one-,  but  sometimes  more  than  one-layered. 
Elongated  oil  tubes  occur  at  the  lateral  angles  of  the  leaves,  but  are 
frequently  not  continuous  from  end  to  end,  so  that  a  cross-section 
often  shows  but  one  or  none.  The  staminate  flowers  are  axillary, 
or  sometimes  terminal,  on  the  branchlets  of  the  preceding  year, 
