A  modification  of  Baeyer's  theory  thus  appears  to  be
necessary.  Erlenmeyer,  long  before  the  experimental  work
on  carbon  monoxide  just  referred  to  was  done,  suggested  that
the  carbonic  acid  in  the  cells  undergoes  a  reduction  which
leads  to  the  formation  of  formic  acid  and  oxygen,  and  that
the  formic  acid  is  further  reduced  to  formaldehyde  and
oxygen : —

1.  H2CO3  =  CH.,02  +  O

2.  CH2O2  =  CHoO  +  O

or  else  that  the  action  is  continuous  and  that  the  carbon
dioxide  and  water  may  directly  give  rise  to  formaldehyde
and  oxygen  : —

CO2  +  H2O  =  CHjO  +  O2

According  to  these  views  either  formaldehyde  or  formic  acid
must  be  produced.
These  substances,  as  is  well  known,  are  poisonous,  so  that,
if  formed,  they  must  be  polymerized  before  they  have  time  to
injure   the    protoplasm,    and    experiments   have   shown   that

•Kraschennikoff:  "Rev.  Gen.  Bot.,"  1909,21,  177.
tSulander:  "  Beih.  bot.  Centrbl.,"  1909,  24,  I,  357.
FORMALDEHYDE  IN  GREEN  LEAVES       157

under  certain  conditions,  formaldehyde  may  be  made  use  of
by  the  plant.  Thus  Bokorny*  showed  that  Spirogyra  can
make  starch  when  supplied  with  a  compound  of  formaldehyde
and  sodium  hydrogen  sulphite ;  also  Treboux  f  and  Bouilhac
have  stated  that  Ebdea,  Sinapis,  and  certain  Algae  can  form
starch  in  the  dark  when  supplied  with  dilute  (-0005  per  cent)
solutions  of  formaldehyde.
In  this  connexion  Grafe's  J  results  are  important,  for  he
found  that  if  green  seedlings  be  grown  in  the  light  in  an
atmosphere  containing  no  carbon  dioxide  but  formaldehyde
vapour  (not  more  than  i'3  per  cent),  they  show  a  greater
increase  of  growth  and  in  dry  weight  as  compared  with
controls  grown  under  the  same  conditions,  but  without  the
formaldehyde.
