A  ocSbertPi8w'm'}    Structure  of  Heuchera  Americana.  471 
possesses  a  tetrarch  radial  bundle.  One  of  the  original  xylem  rays  is 
shown  at  d,  and  the  other  three  at  df,  dn  and  d,n ',  respectively.  At 
g  and  h,  are  two  of  the  four  secondary  xylem  masses,  which,  to  the 
naked  eye,  in  a  cross-section  of  the  root,  present  the  appearance  of 
a  cross. 
The  ducts  and  tracheids  of  the  xylem,  both  of  the  rhizome  and 
roots,  are  nearly  all  of  the  scalariform  variety,  and  the  component 
cells  of  a  row  of  tracheids,  or  of  a  duct,  as  the  case  may  be,  are 
short  and  oblique-ended,  or  taper-ended,  as  shown  in  Fig.  5.  In 
consequence  of  their  shortness  and  the  markings  on  the  oblique 
end-walls,  an  unusual  number  of  the  tracheids  show  the  scalari- 
form markings  when  viewed  in  cross-section. 
These  markings,  as  they  appear  in  this  view,  are  indicated  in 
Fig.  4.  at  g,  and  in  various  other  of  the  tracheary  elements,  shown 
in  the  same  figure. 
Fig.  6. 
Starch  is  abundant  in  both  the  rhizome  and  the  roots  in  most  of 
the  mature  parenchymatous  cells.  The  starch  is  small-grained  and 
the  grains  are  mostly  simple,  smooth  and  rounded  or  oblong- and 
usually  destitute  of  any  very  distinct  markings.  Only  the  largest 
grains  show  a  fissure  at  the  central  or  sub-central  hilum.  Some- 
times these  fissures  have  several  rays  and  sometimes  they  consist  of 
a  single  slit.  Bi-  or  tri-nucleated  grains  are  not  uncommon  and 
double  or  multiple  grains  sometimes  occur.  Concentric  markings 
are  seldom  or  never  observable  even  in  the  larger  grains,  except  by 
the  aid  of  swelling  reagents,  and  even  then  with  difficulty.  Only 
