464  boussingalt's  researches  on  the  action  of  foliage. 
and  the  experiments  pretty  clearly  show  that  they  lose  it  through 
the  deleterious  action  of  the  vapor  of  mercury.  It  is  thought 
remarkable  that  the  leaf  does  not  under  these  circumstances  at 
all  lose  the  power  of  transforming  oxygen  into  carbonic  acid  ; 
but  that  is  what  we  should  expect,  for  the  carbonic  acid  so 
evolved  (whether  its  evolution  be  called  respiration  or  not)  must 
be  a  product  of  decomposition  of  the  leaf's  contents  or  substance. 
We  owe  to  Boussingault  and  his  assistant  Lewy  the  idea  of 
determining  the  composition  of  the  air  contained  in  a  fertile  soil, 
and  the  fact  that  this  air  in  a  strongly  manured  soil  contains  a 
very  large  percentage  of  carbonic  acid.  Boussingault  has  now 
devised  an  experiment  by  which  the  air  contained  in  a  branch 
of  an  Oleander  in  full  vegetation  was  extracted.  It  proved  to 
be  nitrogen  88*01  per  cent.,  oxygen  6*64,  carbonic  acid  5*35 
per  cent.  ;  being  about  the  composition  of  the  air  from  a  well- 
manured  soil.  This  carbonic  acid  carried  into  the  leaves  with 
the  sap,  and  also  that  which  they  may  absorb  directly  from  the 
atmosphere,  decomposed  along  with  water  under  sunlight,  must 
be  the  source  of  the  glucose  (C12H12012)  which  it  is  the  principal 
function  of  foliage  to  produce.  This  glucose,  in  fixing  or  aban- 
doning the  elements  of  water,  becomes  sugar,  starch,  cellu- 
lose, or  other  hydrates  of  carbon,  which,  in  whatever  part  of 
the  plant  accumulated  or  deposited,  and  however  transformed 
or  re-transformed,  must  always  have  originated  from  carbonic 
acid  and  water  in  the  green  parts  of  plants.  In  closing 
his  present  paper  with  some  illustrations  of  this  now  familiar 
view,  Boussingault  announces  that  his  more  recent  experiments 
will  enable  him  to  demonstrate  the  direct  formation  of  saccharine 
matter  by  the  green  parts  of  vegetables  exposed  to  the  light. 
A.  G. 
— Amer.  Jour.  Sci.  and  Arts,  July,  1866. 
