AmAprii;5&arm'}         A  Stu(iy  °f  Starch  Grains.  179 
Does  it  indicate  resting  periods  in  the  growth  of  the  grain,  and  that 
as  each  layer  is  added  there  is  a  strong  demarcation — or  does  it  mean 
that  we  have  layers  differing  in  composition,  etc.?  This  brings  us 
to  consider  the  composition  of  the  starch  grain  and  the  meaning  ol 
the  different  layers.  If  we  consult  any  of  the  standard  works  on 
organic  chemistry,  we  find  the  formula  for  starch  given  as  C6H10O5. 
This  formula  gives  us  simply  the  proportion  of  the  elements  carbon, 
hydrogen  and  oxygen,  without  any  scientific  or  practical  information 
in  regard  to  either  its  physical  or  exact  chemical  composition.  On 
the  other  hand,  the  starch  grain  has  been  the  subject  of  much  inter- 
esting investigation  by  botanists.  In  fact,  what  is  to  be  considered 
one  of  the  greatest  intellectual  feats  of  the  century  was  the  study  of 
the  starch  grain  by  C.  Nageli.  Previous  to  this  time  several  hy- 
potheses had  been  given  as  to  the  origin  of  starch  grain  :  (1)  It  was 
considered  to  be  a  bubble  filled  with  a  liquid  ("  Flussigkeit  gefullten 
Blase  ").  (2)  Then  it  was  considered  (1 834)  that  from  a  centric  or  ec- 
centric point,  layer  after  layer  was  added.  (3)  Payen  (1838)  conceived 
the  idea  that  growth  took  place  from  the  outside  towards  the  centre. 
(4)  By  others  (1845)  it  was  considered  that  growth  of  the  starch 
grain  was  like  that  of  the  cell  wall.  Nageli,  in  1858,  announced 
that  growth  of  the  starch  grain  was  effected  by  the  interpolation  of 
new  material  among  the  particles  already  formed.  He  advanced  the 
idea  that  the  starch  grain  consisted  of  elementary  particles  or  mole- 
cules which  were  made  up  of  atoms  (Starkeatome  or  starch  atoms) 
consisting  of  C,  H  and  O. 
Later,  inasmuch  as  the  term  molecule  was  being  employed  by 
chemists  to  mean  something  different  from  what  he  had  in  mind,  he 
invented  the  term  micella,  meaning  thereby  that  each  micella  con- 
sisted of  larger  or  smaller  numbers  of  chemical  molecules.  These 
micellae  were  described  by  him  from  the  interference  of  colors  ob- 
served with  the  polariscope  as  being  "  biaxial  crystals  and  he  assigned 
to  them  as  a  probable  form,  that  of  parallelopipedal  prisms  with 
rectangular  or  rhomboid  bases,"  He  said  each  micella  has  a  watery 
film  (Wasserhulle)  and  is  surrounded  by  a  mother  liquor  which  is 
different  in  composition  from  the  micellae.  The  latter,  with  their 
watery  films,  are  "  held  together  by  the  following  forces:  (1)  The 
attraction  of  the  micellae  for  each  other,  a  force  which  varies  in- 
versely as  the  square  of  the  distance  between  them ;  (2)  the  attrac- 
tion of  each  micella  for  the  water  which  surrounds  it,  a  force  which 
