6  Structure  of  Sangninaria  Canadensis.  {ATanuaryPi895rm' 
this  re-investigation  of  the  subject.  Fresh  materials  were  procured 
and  a  large  number  of  sections,  longitudinal  and  transverse,  of  the 
rhizome  were  made  and  carefully  studied  with  the  view  of  ascertain- 
ing with  certainty  whether  or  not  milk-tissue,  in  the  proper  sense  of 
the  term,  really  does  exist  in  the  rhizome. 
The  red  or  orange-colored  secretion  is  without  doubt  chiefly  con- 
tained in  distinct  cells,  which  are  either  isolated  or  connected  into 
C 
Fig.  3. 
irregular  chains  and  distributed  among  the  parenchymatous  tissues 
of  the  middle  bark  and  large  pith.  But  in  the  inner  portion  of  the 
middle  bark,  and  in  the  inner  bark,  occur  chains  of  cells  which  are 
longer,  more  regular  and  contain  a  yellow  rather  than  an  orange-red 
secretion.  The  cells  composing  the  chains  are  also  much  narrower 
and  more  elongated  than  are  the  ordinary  secretion  cells.  Among 
