AmjJu0iy?i?8h9arm'}  The  Genus  Psoralea..  347 
Ci  The  plant  is  the  pomme  de  prairie  or  pomme  blanche  of  the  early 
Canadian  voyageurs;  the  prairie  turnip  or  prairie  potato  of  the 
American  settlers  ;  the  tipsinah  of  the  Sioux,  and  the  taahgu  of  the 
Osage  Indians. 
"  Description  :  Perennial ;  roughish  hairy  all  over ;  stem  stout, 
erect,  somewhat  branched,  from  5  to  15  inches  high,  growing  from  a 
tuberous  root ;  leaves  on  long  petioles,  palmately  5-foliolate,  the 
obtuse  leaflets  obovate,  oblanceolate  or  oblong,  about  1  \  inches  long  } 
stipules  free,  lanceolate ;  flowers  appearing  in  June  and  July  in  dense 
thick  spikes  about  2  inches  long,  borne  on  peduncles  2  to  3  inches 
long,  exceeding  the  petioles ;  each  three-flowered  cluster  subtended  by 
a  large  bract ;  lobes  of  calyx  lanceolate,  acuminate,  4  to  6  lines  long, 
equal  to,  or  larger  than,  the  gibbous  tube,  and  but  little  shorter  than 
the  purplish  corolla  ;  seed  oval,  3  lines  long,  flat,  smooth  and  shining. 
"  Soon  after  blossoming  the  plant  dries  up  into  a  brown  rigid  mass, 
then  breaks  off  and  becomes  a  "  tumble-weed  "  blown  over  the  prairie, 
scattering  its  seeds  as  it  goes. 
"  The  tuber  is  two  or  three  inches  under  ground.  It  is  irregularly 
elliptical  in  shape,  from  ovoid  to  fusiform ;  in  size  ranging  from  a 
hen's  egg  to  a  large  filbert,  averaging  1 J  to  2  inches  in  length  and  one 
inch  in  diameter.  The  upper  end  shows  the  scars  of  previous  years' 
stems ;  the  lower  end  is  produced  into  a  long  and  very  tough  tap 
root.  It  is  covered  with  a  thick  leathery  skin,  easily  peeled  off  its 
white  and  smooth  surface.  Passing  through  the  axial  line  are  clusters 
of  fibers,  which  proceed  from  the  stem  and  run  into  the  tap  root. 
These  tough,  fibrous  clusters  are  the  only  inedible  part  of  the  skinned 
tubers.  On  section  it  is  seen  to  be  composed  of  a  white  granular  mass, 
at  first  somewhat  spongy,  but  becoming  hard  on  drying,  in  which  state 
it  is  friable  and  easily  pulverized  into  a  light  starchy  flour. 
"  The  prairie  turnip  is  a  widely  distributed  plant.  It  is  found  from 
the  lakes  westward  to  the  Rocky  Mountains,  and  from  the  Saskat- 
chawan  River  downward  to  Louisiana  and  Texas.  It  is  on  the  dry 
table-lands  of  the  Missouri,  however,  from  Montana,  through  Dakota 
and  Nebraska,  to  Kansas,  that  it  is  most  abundant. 
"  The  tuber  of  this  plant  has  always  been  of  great  importance  to 
the  Indians,  one  of  their  vegetable  staple  foods.  It  is  mentioned  by 
all  the  explorers  and  voyageurs  who  first  traded  with  the  Indians  of 
the  Western  prairies.  It  is  in  its  best  condition  when  the  flowers  be- 
gin to  fade,  in  the  latter  part  of  July.    At  that  time  the  squaws  start 
