Am.  Jour.  Pharm. ) 
Oct.,  1881.  j 
Silphium  Laciniatum,  Rosin  Weed. 
487 
SILPHIUM  LACINIATUM,  Lm.,  ROSIN  WEED. 
Natural  order,  ComposUce ;    Sub-order,  Tubuliflorw ;  Sub-tribe, 
^felampodinece. 
By  Lemuel  Iorwertpi  Morris,  Ph.G. 
From  an  Inaugural  Essay. 
Rosin  weed,  or  compass  plant,  is  found  growing  extensively  west- 
ward from  Ohio,  between  38°  to  46°  north  latitude. 
The  stem  is  usually  three  to  six,  but  sometimes  reaches  the  height 
of  ten  feet,  and  bears,  along  its  entire  length,  leaves  similar  to  the 
radical,  but  gradually  becoming  smaller  toward  the  apex.  The  flow- 
ers, borne  in  a  kind  of  raceme  at  the  upper  part  of  the  stem,  are  two 
to  three  inches  broad,  and,  as  in  all  the  other  species,  yellow ;  the 
scales  of  the  involucre  are  ovate,  tapering  into  long  and  spreading 
rigid  points;  achenia  broadly  winged  and  deeply  notched.  There 
arise  from  the  root  numerous  radical  leaves,  wdiich  are  from  ten  to 
thirty  inches  in  length,  very  .rough  with  bristly  hairs,  in  general  out- 
line ovate,  but  deeply  pinnately  cut  and  parted,  the  divisions  them- 
selves very  often  cut-lobed.  The  root  is  from  one  to  three  feet  in 
length,  and  one-half  to  two  inches  in  diameter,  and  has  a  very  rough 
and  irregular  cortical  layer.    Its  anatomical  structure  is  as  follows : 
Fig.  A  shows  a  cross  section  of  the  root ;  the  inner  portion,  com- 
prising one-sixth  of  the  radius  of  the  root,  is  the  pith  (p),  and  is 
composed  of  loose  parenchyma  cells ;  we  then  find  two  circles  of  resin 
(cc)  ducts,  the  inner  circle  near  the  dividing  line  of  the  woody  tissue 
(w)  and  the  pith,  and  the  outer  circle  between  the  wood  wedges  (w) 
and  the  outer  layer  of  parenchyma  (d)  tissue.  These  resin  ducts  are 
very  irregular  in  shape. 
The  woody  zone  between  the  two  rows  of  resin  ducts  is  traversed 
by  very  wide  medullary  rays  ;  the  wood  wedges  are  irregular  in  shape, 
and  at  the  head  of  each  is  a  wedge-shaped  bundle  of  sieve  (s)  tubes, 
reaching  to  the  outer  row  of  resin  ducts.  Between  the  outer  row  of 
resin  ducts  and  the  cortical  (6)  layer  is  found  a  narrow  layer  of  paren- 
chyma cells,  which  are  more  compressed  as  they  near  the  cortical  layer, 
and  this  latter  is  composed  of  very  irregular  compressed  tissue,  resem- 
bling stone  cells,  and  is  af  a  yellowish-green  color. 
a  shows  the  development  of  a  rootlet ;  most  of  the  rootlets  origi- 
nate from  the  inner  row  of  resin  ducts. 
