222 
The  Structure  of  the  Starch  Grain. 
Am.  Jour.  Pharm. 
May,  1907. 
globule,  and  the  other  to  a  body  such  as  an  air  bubble  (or  vesicle 
filled  with  air  or  any  other  gaseous  or  rarefied  material).  The 
appearance  as  observed  in  the  oil  globule  corresponds  to  that  of  the 
layer  next  to  the  point  of  origin  of  growth  and  the  layers  alter- 
nating with  it.  The  appearance  of  the  air  bubble  corresponds  to 
that  of  the  point  of  origin  of  growth  and  the  layers  alternating  with 
it.  There  is  this  difference,  however,  that  instead  of  the  purplish 
hue  so  characteristic  of  the  air  bubble,  there  is  a  reddish  field  in  the 
starch  grain  which  may  be  taken  as  indicating  that  it  is  of  an  entirely 
different  composition.  A  possible  explanation  of  this  phenomenon 
may  be  that  in  the  air  bubble  the  violet  rays,  owing  to  their  length 
and  velocity,  completely  overshadow  the  red  rays ;  whereas  in  the 
starch  grain  the  layers  containing  other  substances  offer  a  resistance 
to  and  refract  the  violet  rays  and  leave  the  red  only  in  view.  As  a 
result  of  this  physical  examination  of  the  grain  we  observe  that  the 
successive  layers  differ  in  density,  and  that  these  correspond  to  the 
"  water-poor"  and  "  water-rich  "  lamellae  described  by  Nageli  (16). 
We  further  find  in  some  of  the  potato  starch  grains  that  at  the 
periphery  of  the  point  of  origin  of  growth,  as  well  as  upon  the 
inside  of  one  or  more  of  the  layers  corresponding  to  it,  there  is  a 
dark  line  much  resembling  the  peripheral  layer  of  the  grain  {fig.  j). 
This  probably  led  Dippel  (22),  Strasburger  (23),  and  Krabbe  (24), 
to  consider  that  the  lamellae  did  not  differ  in  character,  but  that  this 
appearance  of  lamellation  was  due  to  lines  of  contact,  as  already 
stated.  Krabbe  in  the  chapter  dealing  on  the  "  Spiralstreifung  der 
Bastfasern  "  further  distinguishes  between  "  Grenzflachen "  and 
"  Contactflachen."  He  says  :  "  Wo  Schichten  mit  derselben  Strei- 
fung,jedoch  mit  verschiedener  Steilheit  derselben,  vorliegen,  da  wird 
ihre  gegenseitige  Abgrenzung  dadurch  noch  deutlicher,  dass  die 
Grenzflachen  der  Spiralbander  in  der  Contactflache  der  Schichten 
nicht  immer  aufeinander  stossen." 
A  further  evidence  that  there  is  a  marked  difference  in  the  layers 
of  the  grain  is  the  effect  produced  by  staining  reagents  (29,  30). 
On  treating  starch  grains  with  weak  aqueous  solutions  of  safranin 
and  gentian  violet,1  it  is  observed  that  certain  parts  of  the  grain 
take  up  these  stains  more  readily  than  others.    The  gentian  violet 
1  The  method  used  by  the  author  consisted  simply  in  treating  the  freshly 
isolated  starch  grains,  or  the  commercial  starches,  with  weak  aniline  dye  solu- 
tions and  allowing  them  to  dry  at  an  ordinary  room  temperature. 
