AmAprV\i(S9arm-}         A  Study  of  Starch  Grains.  175 
For  instance,  in  white  potato  the  alkaloid  solanine  is  decreased 
whereas  in  cinchona  and  opium  the  alkaloids  are  increased  by  pro- 
cess of  cultivation. 
ORIGIN  AND  FORMATION  OF  STARCH. 
We  now  come  to  consider  the  first  visible  product  of  constructive 
metabolism  of  the  plant,  viz. :  starch.  It  occurs  in  the  plant  as  an 
assimilative  product  and  as  a  reserve  product.  In  the  former  con- 
dition it  is  found  in  all  the  green  parts  of  plants  at  the  close  of  day 
in  the  summer  when  the  sun  has  been  shining  upon  them.  As  a 
reserve  product  it  is  found  in  roots,  rhizomes,  barks,  buds,  fruits  and 
seeds. 
The  assimilative  starch  is  synthetically  produced  from  the  inor- 
ganic compounds,  carbon  dioxide  and  water,  and  results  only  when 
the  chloroplastid  is  present  and  the  plant  is  supplied  with  light 
and  salts  of  potassium.  It  has  been  supposed  that  the  reaction 
may  be  represented  as  follows:  That  5  molecules  of  water  and  6  of 
carbon  dioxide  produce  1  molecule  of  starch  with  the  liberation 
of  6  molecules  of  oxygen. 
There  is  no  doubt  that  there  are  simpler  products  first  formed,  and 
it  is  supposed,  from  the  experiments  of  Bokorny,  that  formaldehyde  is 
one  of  the  primary  compounds.  This  experimenter  removed  all 
starch  from  specimens  of  Spirogyra,  and  then  fed  them  in  the  dark 
with  a  sodium  salt  of  formic  aldehyde.  Starch  was  rapidly  formed 
in  the  chloroplastids,  thus  indicating  the  possibility  that  other  com- 
pounds are  formed  before  we  have  the  product  finally  formed  which 
we  recognize  as  starch. 
It  has  not  been  possible  as  yet  to  demonstrate  the  successive 
steps  in  the  process  of  development  of  starch.  All  that  we  can  say 
is  that  the  production  of  starch  normally  is  dependent  upon  the 
following  conditions,  viz.:  light;  air  containing  C02  and  moisture; 
and  that  the  organ  in  which  it  is  produced  is  the  chloroplastid,  when 
associated  with  protoplasm.  The  chloroplastid  consists  of  a  ground 
substance,  and  a  pigment  which  again  is  made  up  of  a  green 
(chlorophyll),  a  yellow  (xanthophyll),  and  also  a  reddish  fluorescent 
principle.  Very  many  experiments  have,  however,  been  made  to 
determine  what  part  the  chloroplastid  and  protoplasm  play  in  the 
production  of  starch,  and  necessarily  numerous  theories  have  been 
proposed.    One  view  was  (that  by  Sachsse)  that  the  chlorophyll 
