RESEARCHES   ON   THE  RESPIRATION  OF  FLOWERS.  33 
RESEARCHES    ON  THE  RESPIRATION  OF  FLOWERSi 
By  M.  Aug.  Cahours. 
While  the  green  portions  of  plants  under  the  influence  of 
light  effect  the  decomposition  of  carbonic  acid,  of  which  they 
assimilate  the  carbon,  rejecting  the  oxygen  into  the  atmosphere, 
the  colored  parts,  on  the  contrary,  consume  the  oxygen  to  pro- 
duce carbonic  acid.  Thus,  by  one  of  nature's  most  admirable 
harmonies,  the  atmosphere  does  not,  after  ages,  become  sensibly 
modified. 
But  if  experiment  has  long  since  proved  that  flowers  left  in 
atmospheric  air  develop  carbonic  acid  at  the  expense  of  the 
oxygen  it  contains,  it  is,  nevertheless,  interesting  to  determine 
the  modifications  presented  by  this  phenomenon  under  varying 
circumstances. 
Now,  do  all  flowers  of  equal  weight,  or  of  equal  surface  con- 
sume, under  identical  circumstances,  the  same  quantity  of  oxy- 
gen, and  produce  the  same  proportion  of  carbonic  acid  ?  Do 
scented  flowers  behave  in  the  same  way  as  those  which  are 
scentless  ?  Does  the  same  flower  act  more  energetically  on  an 
atmosphere  determined  under  the  influence  of  a  more  or  less 
vivid  light  than  in  perfect  darkness  ?  Is  the  consumption  of 
oxygen  proportionate  to  the  temperature  of  the  medium  in 
which  the  flower  respires  ?  Does  a  plant  consume  the  same 
quantity  of  oxygen  at  each  period  of  its  development?  Finally, 
what  do  the  various  parts  of  the  plant — the  calyx,  corolla,  pistil, 
stamens — respectively  play  ? 
Such  are  the  questions  I  propose  to  resolve. 
If  we  experiment  on  various  flowers  of  equal  weight,  arrived 
at  the  same  state  of  development,  it  is  easy  to  ascertain,  by 
operating  under  perfectly  identical  conditions,  that  the  respec- 
tive consumption  of  oxygen  in  a  given  time  is  far  from  being 
the  same.  As  to  the  more  or  less  powerful  odor  exhaled  by 
the  plant,  it  seems  to  play  but  a  trifling  part  in  the  produc- 
tion of  this  phenomenon ;  In  fact,  a  scentless,  or  nearly  scent- 
less, flower  consumes,  in  a  given  time,  more  oxygen  than  a 
strongly  scented  one.  Results  obtained  at  the  beginning  of 
these  researches  led  me  at  first  to  suppose  that  scented  flowers 
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