522  Structure  of  Geranium  Maculatum.  {^VembefasS1' 
portions  respectively  of  the  secondary  xylem  and  of  the  secondary 
phloem. 
It  would  be  interesting  to  determine  by  the  study  of  specimens 
gathered  at  different  seasons  of  the  year  whether  any  relation  exists 
between  the  amount  of  starch  and  the  amount  of  tannin  in  the 
rhizomes.  Does  the  amount  of  tannin  in  the  rhizome  increase  as 
the  starch  diminishes,  or  is  the  amount  of  starch  totally  independent 
of  that  of  tannin? 
The  starch  of  geranium  is  rather  characteristic.  The  grains  are 
smooth,  mostly  long,  ovate  in  outline,  with  the  hilum  located  near 
the  larger  end.  The  hilum  is  occasionally  fissured,  but  is  usually 
unfissured.  The  grains  are  very  seldom  double,  but  sometimes  bi- 
nucleated.  About  the  hilum  are  a  series  of  curves,  those  nearest  it 
circular  and  concentric  with  it,  while  those  farther  away  are  more 
elliptical  and  eccentric,  and  the  more  eccentric  the  more  remote 
they  are  from  the  hilum.  The  longest  grains  are  about  the  T^-g-th 
of  an  inch  in  length.  The  polarization  cross  is  very  unequal- 
armed,  as  shown  in  a,  Fig.  5. 
DESCRIPTION  OF  FIGURES. 
Fig.  1. — Rhizome  and  roots  of  Geranium  maculatum,  Z.,  natural  size. 
Fig.  2. — Sections  of  a  rhizome  magnified  twelve  diameters. 
A.  Transverse  section;  a,  corky  layer  ;  b,  middle  layer  of  bark  ;  c>  cambium 
zone  ;  d,  vasal  bundle  ;  e,  pith  ;  fy  cluster  of  tannin  cells. 
B.  Longitudinal  section;  a,  corky  layer  ;  b,  middle  layer  of  bark  ;  c,  cam- 
bium zone  ;  d,  pith  ;  e,  cluster  of  tannin  cells  ;  f,  vasal  bundle.  The  sections 
from  which  drawings  were  made  had  been  cleared  of  starch. 
Fig.  3. — Cross-section  of  root  magnified  75  diameters;  a,  corky  layer  ;  b,  pri- 
mary cortex ;  c,  primary  phloem  ;  d,  primary  xylem  ray;  e,  secondary  xylem; 
/,  secondary  phloem;  g,  cambium. 
Fig.  4. — A  few  tannin  and  ordinary  parenchyma  cells  from  pith  of  rhizome 
magnified  375  diameters,  a  and  af  tannin  cells,  also  containing  starch  grains; 
b  and  bf  ordinary  parenchyma  cells. 
Fig.  5. — Starch  of  Geranium  magnified  750  diameters,  a,  one  of  the  grains 
as  viewed  by  aid  of  polarized  light. 
