Am.  Jour.  Pbarm.") 
September,  1894.  J 
Structure  of  Podophyllum. 
421 
The  parenchyma  tissues  of  the  rhizome  show  no  special  peculiari- 
ties.   The  cells  are  throughout  heavily  charged  with  starch  grains. 
The  vasal  bundles  are  the  only  portions  of  the  structure  which 
contain  lignified  tissues  and  here  it  is  almost  confined  to  the  ducts 
of  the  xylem.  These  ducts  are  of  moderate  size,  rather  loosely 
arranged  with  soft  tissues  between,  and  occurring  singly  or  in  groups 
of  a  few.  The  smallest  are  in  the  inner  part  of  the  bundle  and 
nearly  all  are  either  reticulate  or  scalariform,  the  one  form  passing 
into  the  other.  An  occasional  spiral  duct  of  small  size  is  found  in 
the  inner  part  of  the  bundle.  The  other  tissues  of  the  xylem  con- 
sist chiefly  of  wood  parenchyma,  no  wood  cells  being  developed. 
In  the  phloem  of  the  bundles  are  seen  sieve  tubes  of  moderate 
size,  and  companion  cells  along  with  other  parenchymatous  elements. 
In  old  rhizomes  we  find  many  of  the  cells  of  the  phloem  with  the 
walls  collapsed  and  variously  wrinkled.  No  distinct  sheath  is  trace- 
able about  the  bundle. 
Fig.  3  shows  one  of  the  bundles  magnified  175  diameters,  a  is  a 
sieve-plate;  b,  meristem  tissue;  c>  a  duct  in  the  xylem;  d,  a  paren- 
chyma cell  exterior  to  the  bundle;  e,  wood  parenchyma  of  the 
bundle. 
In  the  outer  part  of  the  phloem  there  are  sometimes,  though  not 
always,  found  a  few  cells  of  rather  large  diameter  having  somewhat 
thickened  and  lignified  walls.  These,  when  viewed  in  longitudinal 
section,  are  found  to  consist  each  of  a  single  row  of  elongated  cells, 
which  together  resemble  a  bast  fibre  in  appearance.    They  are,  in 
Fig.  4. 
