Arn,M0ay?i?o7frm*}      The  Structure  of  the  Starch  Grain.  221 
grain  to  be  the  direct  product  of  the  polymerization  of  soluble  carbo- 
hydrates of  either  the  glucose  or  cane-sugar  group,  together  with 
the  abstraction  of  water.  This  process  is  carried  on  under  the  influ- 
ence of  an  organized  body — either  cytoplasm,  or  a  plastid,  or  both. 
The  products  thus  formed  consist  of  two  crystalloidal  substances, 
namely,  starch  cellulose1  and  granulose,  and  also  a  colloidal  sub- 
stance. These  occur  as  follows:  (a)  In  the  point  of  origin  of  growth 
we  find  the  colloidal  substance  associated  with  a  small  proportion  of 
cellulose  as  also  in  the  alternate  lamellae ;  (b)  in  the  other  layers 
occurs  the  granulose  associated  with  a  small  amount  of  colloidal 
substance  and  possibly  also  some  cellulose  ;  (c)  the  peripheral  layer 
of  the  grain  is  not  readily  acted  upon  by  reagents  and  is  quite  elastic 
and  more  or  less  porous,  probably  consisting  of  an  anhydride  of 
cellulose;  (d)  in  some  cases  some  of  the  dextrins  or  some  of  the 
non-colloidal  or  crystalline  carbohydrates,  as  maltose,  dextrose, 
levulose,  etc.,  may  be  present,  but  these  are  probably  formed  as  a 
result  of  alterations  taking  place  in  the  grain. 
There  have  been  a  number  of  important  contributions  on  the  sub- 
ject of  the  origin  and  structure  of  the  starch  grain,  and  while  the 
views  of  the  authors  appear  to  be  more  or  less  at  variance,  still  this 
is  not  to  be  wondered  at,  and  it  is  highly  probable  that  future  obser- 
vations will  harmonize  some  of  these  conflicting  views. 
The  illustrations  of  potato  starch  grains  in  the  different  text- 
books show  two  kinds  of  grains,  one  in  which  the  point  of  the 
origin  of  growth  and  alternate  lamellae  are  light  in  color,  as  figured 
by  Sachs  (26);  and  another  in  which  the  corresponding  parts 
are  dark  in  color,  as  figured  by  Strasburger  (27).  There  is  in 
reality  no  difference  in  these  grains,  this  apparent  difference  being 
due  to  the  manner  of  focusing  upon  them  {figs,  r,  2),  that  is, 
whether  viewing  the  lamellae  from  above  or  from  below,  or,  as  the 
Germans  would  say,  by  "  tiefe  oder  hohe  Einstellung."  The  two 
views  of  the  successive  lamellae  thus  obtained  may  be  compared  to 
the  appearances  obtained  with  two  entirely  different  substances,  the 
one  corresponding  to  a  more  or  less  definite  body,  as  an  oil 
1  Cellulose  was  a  term  first  applied  by  Nageli  (16)  and  corresponds  to  trie 
farinose  of  Von  Mohl  (20)  and  probably  to  the  /3-amylose  of  Arthur  Meyer  (21). 
Granulose,  another  term  which  is  generally  accepted  to  have  been  coined  by 
Nageli  (16),  was  adopted  by  Von  Mohl  (20)  and  apparently  corresponds  to  the 
a-amylose  of  Arthur  Meyer  (21). 
