220  the  Structure  of  the  Starch  Grain.      { Am •£™;1%gtm~ 
the  micellae  already  formed,  and  also  in  forming  new  micellae,  which 
develop  and  arrange  themselves  according  to  the  laws  which  the 
micellae  previously  formed  have  obeyed.  This  theory  is  known  as 
the  "  intersusception  theory,"  while  the  earlier  one  is  spoken  of  as 
the  "  apposition  theory."  In  addition  to  these  two  views  in  regard 
to  the  structure  of  the  starch  grain,  Schimper  (17)  considered  that 
it  is  made  up  of  sphere-crystals  which  he  called  u  Spharokrystalloide." 
Meyer  (21)  has  enlarged  upon  this  view  and  considers  the  starch 
grain  to  be  made  up  of  two  kinds  of  acicular  crystals,  which  he  calls 
"  Trichiten,"  these  being  composed  of  a  amylose  and  /3-amylose, 
there  being  also  present  in  the  grains  that  are  colored  red  with 
iodine,  amylodextrin  and  dextrin.  He  further  says  that  most  starch 
grains  consist  altogether  or  nearly  so  of  amylose,  and  that  these  are 
colored  blue  with  iodine.  These  latter  starch  grains  are  made  up 
of  sphere  crystals  of  amylose,  arranged  in  layers,  and  these  layers 
may  consist  of  crystals  of  either  a-amylose  or  j3  amylose,  or  both, 
some  starch  grains  containing  in  addition,  as  already  stated,  large 
amounts  of  amylodextrin  and  dextrin. 
Starch  grains  are  distinguished  from  one  another  by  the  following 
particulars  :  (1)  The  origin  in  the  plant  ;  (2)  the  shape  of  the  grain ; 
(3)  the  size  of  the  grain;  (4)  the  position  of  the  point  of  origin  of 
growth;1  (5)  the  shape  of  the  point  of  origin  of  growth;  (6)  dis- 
tinctness of  lamellae ;  (7)  the  direction  of  the  lamellae  ;  (8)  behavior 
toward  dilute  iodine  solutions ;  (9)  the  temperature  at  which  the 
"  Kleister  "  or  paste  is  formed  and  its  consistency ;  (10)  the  behavior 
towards  various  reagents,  as  chromic  acid,  calcium  nitrate,  chlor-zinc- 
iodide,  sulphuric  acid,,  diastase,  etc. ;  (11)  the  appearance  as  viewed 
by  polarized  light.  These  differences  in  starch  grains  not  only  from 
different  sources,  but  even  in  those  of  the  same  origin,  tend  to  show 
that  instead  of  starch  being  a  uniform  substance,  it  is  made  up  of 
several  substances,  these  occurring  in  varying  proportions  but  ap- 
pearing to  be  more  or  less  definitely  arranged. 
The  author  may  briefly  state  that  he  conceives  the  reserve  starch 
1  The  terms  "hilurn"  and  "  nucleus  "  have  been  employed  to  distinguish 
the  central  or  excentral  marking,  around  which  the  lamellae  or  layers  of  the 
grain  are  arranged.  These  terms,  however,  are  open  to  criticism,  inasmuch  as 
they  are  employed  for  other  and  specific  purposes.  The  expression  "point  of 
origin  of  growth  "  seems  to  be  better  on  account  of  its  being  less  confusing, 
and  is  moreover  descriptive  and  accurate. 
