^eJXrflm'}        Odorous  Products  in  Plants.  553 
in  this  case  the  whole  of  the  essential  oil  will  exist  in  the  free  state 
in  the  green  organs. 
In  other  cases,  the  glucoside  only  comes  in  contact  with  the  f  er-  • 
ment  which  is  capable  of  splitting  it,  in  the  flower.  It  will  then 
only  be  after  it  has  circulated  as  far  as  the  flower,  undergoing  in 
its  course  more  or  less  profound  modifications,  that  it  will  be  able  to 
liberate  the  constituents  of  the  essential  oil,  and  the  flower  alone 
will  be  odorous.  It  is  not  impossible  that,  in  certain  flowers,  the 
medium  may  be  so  favorable  to  the  splitting  up  of  the  glucoside,  that 
the  latter  is  completely  split  up  as  soon  as  it  arrives  there.  The 
formation  of  further  quantities  of  essential  oil  in  certain  flowers  in 
proportion  as  the  essential  oil  already  formed  is  removed,  would  be 
explained  by  a  phenomenon  of  chemical  equilibrium.  The  following 
reaction :  Glucoside  +  Water  =  Glucose  +  Essential  Oil,  would  be 
restricted  by  the  reverse  reaction,  and  a  state  of  equilibrium  would 
be  reached  when  the  glucose  and  the  essential  oil  would  amount  to  a 
certain  proportion.  Thus  the  flowers  in  question,  if  left  to  them- 
selves, would  retain  a  quantity  of  perfume  which  would  not  increase. 
On  the  other  hand,  if  the  essential  oil  be  removed  as  fast  as  it  is 
formed,  the  decomposition  of  the  glucoside  would  no  longer  be 
limited,  and  it  would  continue  to  take  place.  Consequently,  the 
appearance  of  a  fresh  quantity  of  perfume  in  the  plant  whose  life 
is  prolonged  whilst  the  odorous  matter  is  continuously  removed, 
follows  as  the  result  of  a  phenomenon  of  chemical  equilibrium  in  the 
vegetable  cell. 
The  type  reactions  will  serve  as  an  explanation  of  the  changes : 
R-OH  ->  RCHO  ->  R-COOH  +  (H20)n 
R-OH  +  R-COOH  ->  R-COOR  +  (H20)n 
R-CHOH  — -»  R-CO.R  +  (H20)n — accounting  fo  the  formation  of  alcohols  and 
phenols  and  their  aldehyds,  acids,  esters  and  ketones,  etc. 
It  will  be  understood,  without  it  being  necessary  to  insist  on 
it,  what  advantage  we  have  been  able  to  derive  from  the  practical 
standpoint  as  regards  the  value  and  the  yield  of  perfume,  from  all 
these  results  obtained  by  scientific  research. 
Physiological  Role  of  the  Odorous  Matter. — In  collaboration  with 
M.  Hebert,  I  have  proved  that,  contrary  to  what  was  previously 
believed,  the  odorous  kinds  of  matter  are  not  waste  products  of  which 
the  plant  cannot  make  use.  They  are  capable  of  being  utilized  by 
the  plant,  particularly  when  the  latter  is  protected  from  light  and  no 
