38  THE  PEPPERMINT  PLANTATIONS  OF  MICHIGAN. 
from  the  joints,  form  a  superficial  network  over  the  whole  field, 
suppressing  every  other  weed,  and  leaving  no  means  of  subduing 
this  weed,  without  injuring  the  crop.  This  weed  is  known  by 
the  several  names  of  Horse-tail  weed,  Qows-tail,  Mares-tail, 
Fieldbroom,  Bitterweed,  and  Fireweed;  its  botanical  name,  Er#ch- 
■  thites  liieracifolius.  It  grows  throughout  the  United  States 
in  moist  woods,  and  in  the  rank  soil  of  recent  clearings  ;  its 
odor  is  peculiar,  and  somewhat  disagreeable,  depending  upon  a 
volatile  oil.  It  is  employed  somewhat  in  medicine,  particularly 
by  the  Eclectics.  This  plant,  after  it  gains  a  foothold  in  the 
Mint  field,  the  third  year,  is  accompanied  by  June  grass,  both 
of  which  are  cut  with  the  Mint  and  go  into  the  process  of  dis- 
tillation with  it.  The  Fireweed  yields  an  essential  oil  of  no 
value,  which  is  pungent  and  somewhat  bitter.  It  is  the  only 
plant  which  grows  with  the  Mint  that  yields  an  essential  oil. 
It  is  somewhat  difficult  to  detect  in  the  Mint  oil,  unless  mixed  in 
the  ratio  of  more  than  fifty  per  cent.,  except  by  the  specific 
gravity  of  the  mixed  oil ;  the  pure  Fireweed  oil  requires  eigh- 
teen fluid  ounces  to  weigh  one  pound  avoirdupois,  L  e.  a  quantity 
of  weed  oil  equal  to  one  pound  of  Mint  oil  in  bulk  weighs  but 
fourteen  ounces  avoirdupois. 
It  will  be  seen  from  the  foregoing  that  this  weed  oil  finds  its 
way  into  a  very  large  proportion  of  the  oil  of  Peppermint  pro- 
duced, either  by  accident  or  design.  It  has  indeed  often  been 
used  by  unscrupulous  persons  and  producers  in  adulterating 
their  Mint  oil ;  some  have  been  known  to  distill  it  pure,  for  that 
purpose,  from  the  weed  gathered  in  waste  fields  and  fallow 
grounds. 
The  Fireweed  oil,  spirits  of  turpentine  and  high  proof  alcohol 
constitute  the  only  materials  known,  that  are  used  in  adulterat- 
ing the  pure  Mint  oil ;  though  it  may  be  presumed  that  bland 
fixed  oils  are  often  used  for  the  same  purpose.  The  odor,  and 
less  specific  gravity  of  the  weed  oil  best  serves  to  detect  its 
presence  in  Mint  oil,  as  also  that  of  turpentine.  Washing  it 
with  water  will  remove  the  greater  portion  of  the  alcohol  from 
oil  adulterated  with  it.  Any  fixed  oil  contaminating  it,  is  de- 
tected by  the  greasy  stain  such  mixed  oil  leaves  upon  paper,  and 
is  removed  by  re  distillation.  The  specific  gravity  of  pure  oil 
Peppermint  when  fresh  is  0-902. 
