ON  THE  MATURATION  OF  FKUITS. 
231 
We  have  experimented  on  the  common  orange,  one  of  the 
fruits  which 'most  distinctly  shows  the  period  of  maturation. 
The  structure  of  the  orange,  the  clear  distinction  between  its 
various  parts,  the  thickness  of  its  rind,  which  effectually  iso- 
lates its  juice,  and,  lastly,  the  relatively  rapid  period  of  its  ar- 
tificial maturation,  offer  especial  facilities  for  observation. 
The  chemical  composition  of  the  juice  of  the  orange  adds  to 
these  facilities.  In  fact,  the  juice  is  principally  composed  of 
citric  acid,  fermentable  sugars,  and  nitrogenous  principles.  The 
gelatinous  substances  analogous  to  pectin,  which  play  so  impor- 
tant a  part  in  the  maturation  of  certain  other  fruits,  as  M.  Fre- 
my's  researches  have  shown,  exist  in  the  orange,  on  the  contra- 
ry, in  very  insignificant  proportions. 
The  following  is  our  method  of  operating  : — We  take  a  cer- 
tain number  of  green  oranges,  susceptible  of  the  ripening  pro- 
cess, and  distribute  them  in  two  series,  one  comprising  the  riper 
oranges,  the  other,  those  less  ripe,  putting  aside  a  few  from  each 
series  for  analysation.  We  then  leave  them  for  a  few  weeks  in 
a  dry  place,  maintained  at  a  gentle  temperature.  At  the  expi- 
ration of  this  time,  if  the  maturation  is  effected,  we  repeat  the 
analysis. 
In  each  of  these  analyses  we  have  effected  the  following  de- 
terminations : — 
1.  Weigh  each  orange. 
2.  Separate  it  into  four  parts,  viz.,  rind,  seeds,  juice,  and 
pulp.  Weigh  these  four  parts,  and  determine  the  quantity  of 
water  and  residue,  fixed  at  100*^  C,  they  contain. 
3.  Determine  how  much  azotised  and  mineral  matter,  soluble 
in  ether,  the  dried  rind  contains. 
4.  Determine  how  much  azotised  and  mineral  matter  is  con- 
tained in  the  pulp. 
5.  Pursue  the  same  plan  with  the  seeds,  after  determining  the 
number  and  the  mean  weight. 
6.  Estimate  the  quantity  of  water,  citric  acid,  inverted  su- 
gar, cane  sugar,  and  azotised  and  mineral  matter  contained  in 
the  juice. 
Relying  on  these  determinations,  the  total  composition  of  the 
orange  may  be  as(!ertained  with  sufiicient  exactitude,  and  the 
variations  undergone  by  the  principles  it  contains  compared. 
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