244 
Powdered  Drugs  under  the  Microscope. 
Am.  Jour.  Pharm, 
June,  1876. 
will  take  up  the  water,  and  the  iodine  solution  will  come  in  to  take  its 
place.  The  color  of  the  starch  grains  affected  by  iodine,  although 
usually  blue,  may  vary,  according  to  the  amount  of  the  iodine,  from  a 
light  violet,  through  blue,  to  blue-black. 
Under  the  micros- 
cope the  starch-grains 
present  the  form  of 
minute  grains,  of  a 
form  and  structure 
characteristic  for  each 
species.  They  are  us- 
ually bounded  bycurved 
surfaces,  —  spherical, 
elliptical,  egg  -  shaped^ 
lens-shaped,  etc.,  but 
sometimes  they  have 
flat  surfaces  as  well. 
They  usually  contain 
a  dark  spot,  line  or 
cross  within,  which  is 
sometimes  central, 
sometimes  eccentric. 
This  spot  is  called  the 
nucleus  and  is  usually  small  and  round  in  starch  found  in  fresh  tissues^ 
slit  or  cross-shaped  in  grains  which  have  been  dried  (Fig.  i).1 
The  position  and  character  of  the  nucleus  affords  a  valuable  means 
of  describing  the  grains.  The  grains,  also,  frequently  show  a  series 
of  rather  faint  lines  concentric  about  the  nucleus.  When  present,, 
they  sometimes  can  be  distinguished  only  with  careful  focussing  and 
close  examination,  and  in  many  starches  they  are  entirely  absent. 
Sometimes  the  grains  have  more  than  one  nucleus  (Fig.  1,  a)  in  which 
case  they  are  said  to  be  compouud.  The  compound  grains  may  con- 
sist of  only  two  simple  ones,  as  in  tapioca,  or  three,  as  usually  in 
sago,  or  of  a  great  many,  as  in  rice,  oat  and  buckwheat.2 
1  All  the  figures  in  these  papers  were  drawn  from  nature,  by  Louisa  M.  Reed,  of 
Ann  Arbor,  Mich.,  whose  work  is  accurate  and  careful,  as  can  be  tested  by  com- 
paring it  with  the  actual  objects. 
2  For  those  who  wish  to  study  the  microscopical  characters  of  starch  more  in 
Fig. 
.  Grains  of  potato  starch,  a  and  £are  from  a 
fresh  potato,  the  others  have  been  dried. 
