Am.  Jour.  PrjarrrO 
September,  1S94.  / 
Structure  of  Podophyllum, 
419 
Other  small  buds  may  also  be  found  in  the  axils  of  some  of  the 
lateral  scales,  destined  to  give  rise  to  rhizome  branches. 
The  roots  have  a  diameter  when  fresh  of  about  one-sixteenth  of 
an  inch  at  their  base,  are  four  or  five  inches  long,  and  branch  rather 
sparingly  near  their  origin,  quite  freely  toward  their  apex. 
A  cross-section  of  the  rhizome  made  at  some  point  between  the 
swollen  nodes  shows  a  large  pith,  a  circle  of  wood  bundles,  the  mem- 
bers of  which  are  but  little  longer  in  the  radial  than  in  the  tangen- 
tial direction  even  in  old  rhizomes,  a  rather  thick  cortex  consisting 
mostly  of  parenchyma,  but  with  occasional  small  vasal  bundles  and 
a  thin  layer  of  not  very  well-developed  collenchyma  beneath  the 
epidermis  or  the  cork  that  has  taken  its  place.  The  vasal  bundles  in 
Fig.  2. 
the  circle  are  not  equidistant.  Some  are  quite  isolated  from  the  rest, 
being  separated  laterally  from  the  adjacent  ones  by  broad  layers  of 
parenchyma,  while  others  are  crowded  together  in  twos,  threes  or 
fours,  with  very  narrow  layers  of  parenchyma  between.  Some  also  are 
quite  large,  others  relatively  small,  and  some,  especially  the  smaller 
ones,  are  a  little  exterior  to  the  main  circle.  The  number  of  bundles 
may  be  as  many  as  thirty-six ;  the  average,  perhaps,  is  not-  over 
twenty. 
Fig.  1  shows  the  transverse  section  of  a  rather  large  rhizome, 
magnified  six  diameters,  a  is  the  corky  layer;  b,  one  of  the  vasal 
bundles  in  the  circle ;  c}  a  smaller  bundle,  slightly  displaced  from 
the  principal  circle  ;  d  is  a  small  bundle  in  the  cortex. 
It  should  be  remarked  that  the  abave-ground  stem  possesses  a 
