304 
Oils  of  Erigeron  and  Fireweed. 
J  Am.  Jour.  Pharm. 
\       June,  1887. 
after.  Its  height  varies  from  two  to  six  feet,  having  a  single  stalk 
with  a  diameter  of  from  three- fourths  to  one  and  one-half  inches,  and  a 
bright  green  leaf  from  one  to  two  inches  in  width  and  from  three  to 
eight  inches  in  length.  Its  flowers  appear  only  near  the  top,  and  when 
mature,  are  covered  with  fine  white  down,  much  resembling  that  of  the 
common  thistle,  which  is  carried  by  the  wind  to  a  great  distance.  The 
effect  of  the  maturing  of  the  plant  and  its  coming  into  flower  is  so 
marked  that  the  yield  of  essential  oil  is  decreased  thereby  within  a 
single  week  fully  50  per  cent.  ;  and  indeed,  if  the  plant  is  not  cut 
promptly  at  maturity,  the  yield  of  essential  oil  is  only  about  one- third 
of  what  it  would  have  been  two  weeks  preceeding.  The  fireweed 
plant  has  a  most  thrifty,  robust  and  glossy  appearance,  and  is  never 
seen  in  the  peppermint  plantations,  excepting  in  the  rarest  instances, 
and  then  is  usually  found  growing  singly. 
The  erigeron  canadense  is  entirely  distinct  in  its  nature,  growing 
almost  entirely  in  open  stubble  fields  and  "  summer  fallows,"  and 
along  the  roadside,  its  stalks  scarcely  ever  exceeding  a  half  or  three- 
fourths  inch  in  diameter,  and  the  leaves  scarcely  a  half  inch  in  width, 
and  two  or  three  in  length.  Its  flowers  are  very  minute,  and  are  dis- 
tributed more  uniformly  over  the  surface  of  the  plant.  Erigeron  is 
much  richer  in  essential  oil  than  fireweed,  the  former  sometimes 
yielding  over  20  lbs. of  essential  oil  to  a  charge  of  2000  lbs.  of  plants. 
The  yield  of  fireweed  seems  to  average  about  50  per  cent,  of  that  of 
erigeron,  the  plants  being  distilled  under  like  favorable  conditions. 
Now  as  to  the  characteristics  of  their  essential  oils :  Unfortunately, 
most  of  the  physical  tests,  and  the  reagents  usually  employed  in  such 
analyses  do  not  give  as  widely  varying  results  between  these,  as  be- 
tween most  other  oils ;  but  when  submitted  to  spectral  analysis,  I  find 
fortunately,  a  test  which  is  quite  decisive,  and  this  accordingly  has 
the  greater  prominence ;  but  others  more  easily  operated  and  equally 
as  certain,  if  due  precautions  are  taken,  are  also  given. 
First,  eight  samples  of  natural  oil  of  erigeron  were  operated  upon, 
(the  natural  oil  being  taken,  as  it  is  this  quality  which  has  hitherto 
been  mostly  known  in  commerce.)  For  the  purpose  of  showing  the 
relationship  between  specific  gravity  and  polarization,  these  two  tests 
are  given  in  conjunction  with  each  other.  The  polar iscope  used  is  a 
"  Mitscherlich,"  with  a  perception  tube  200  mm.  in  length,  made  by 
De  Sage  of  Heidelberg,  being  the  instrument  referred  to  in  the  first 
article  of  this  series,  (in  the  April  No.  of  the  American  Journal 
