Am.  jour.  Piiarm.  \ 
February,  1914.  J 
The  Starch  Grain. 
83 
ways.  When  starch  is  treated  with  certain  chemicals,  or  heated 
with  water  alone  to  a  temperature  of  6o°  C,  the  grains  show  a 
series  of  successive  changes.  First,  the  lamellae  or  layers  become 
more  distinct,  and  the  layers  appear  to  be  made  up  of  parallel 
crystal-like  particles,  these  latter  being  more  numerous  in  suc- 
cessive alternate  lamellae.  Then  as  the  grain  swells  clefts  which 
radiate  from  the  centre  are  formed.  Later  the  centre  of  the  grain 
becomes  hollow,  and  when  the  grain  has  swollen  to  about  four 
times  its  original  size  the  outer  membrane  breaks  and  the  con- 
tents are  gradually  dissolved. 
Some  striking  effects  are  also  produced  when  starch  is  carefully 
treated  with  aniline  dyes.  The  point  of  origin  of  growth  and  the 
successive  layers  alternating  with  it  take  up  the  stains,  thus  again 
showing  the  distinct  character  of  the  two  kinds  of  lamellae  making 
up  the  grains.  When  plant  material  containing  mucilage  is  treated 
with  aniline  stains,  the  stain  is  taken  up  only  by  the  cells  containing 
mucilage,  and  this  indicates  that  the  lamellae  in  a  starch  grain 
which  take  up  the  stains  are  composed  chiefly  of  colloidal  sub- 
stances. From  these  observations  it  is  apparent  that  the  grains 
of  certain  of  the  starches,  as  the  potato,  if  not  of  all  the  lamellated 
starch  grains,  are  made  up  of  two  kinds  of  lamellae,  one  rich  in 
colloids  and  one  rich  in  crystalloids.  The  presence  of  two  kinds  of 
lamellae,  at  least  in  certain  of  the  starch  grains,  and  their  difference 
of  composition  are  further  shown  by  the  use  of  a  weak  solution 
of  iodine,  the  so-called  crystalloidal  layers  or  lamellae  taking  up  the 
iodine  and  becoming  blue.2 
Recently  I  have  been  conducting  some  experiments  to  deter- 
mine further  the  effects  of  heat  upon  the  structure  of  the  starch 
grain.  When  starch  alone  is  heated  to  between  45 °  and  500  C.  from 
15  to  30  minutes,  the  lamellae  and  the  crystalloidal  structure  of  the 
grains  are  brought  out.  The  grain  is  so  resistent  that  the  inner 
structure  does  not  appear  to  be  lost  until  a  temperature  of  over 
1250  C.  is  attained.  Between  1400  and  1600  C.  the  polarization  effects 
of  the  grains  become  faint,  except  in  the  case  of  potato  starch, 
which  now  in  addition  gives  chromatic  effects.  At  2400  C.  all  of  the 
grains  are  disintegrated  except  those  of  corn  starch,  the  individual 
grains  of  which  are  of  a  brownish-yellow  color  and  not  perceptibly 
2Kraemer,  Bot.  Gazette,  Vol.  XXXIV,  Nov.,  1902 ;  Ibid.,  Vol.  XL,  Oct., 
1905;  reprinted  in  Amer.  Jour.  Pharm.,  Vol.  79,  1907,  pp.  217-229;  412-418. 
