870  Growing  Medicinal  Plants  in  America.  { AmDJe°cur'I9PI8arm' 
the  plants  grow  in  their  native  habitat,  and  considerable  investment 
of  money.  Drug  plants  have  been  raised  on  an  experimental  scale 
by  the  government  and  in  the  drug  gardens  of  various  colleges,  but 
it  is  a  very  different  undertaking  to  raise  them  on  a  commercial 
scale.  American  growers  of  crude  drugs  were  confronted  with  the 
necessity  of  increasing  the  value  of  the  plants  in  order  to  overcome 
the  high  cost  of  cultivation.  It  was  soon  found  that  cross-pollina- 
tion would  not  produce  plants  containing  more  active  constituents 
Fig.  6.    A  field  of  cannabis. 
than  they  do  normally,  but  by  careful  selection  of  seed  it  has  been 
possible  to  increase  the  amount  of  active  constituents  in  such  plants 
as  belladonna,  digitalis,  etc.,  to  three  of  four  times  what  the  Pharma- 
copoeia requires.  Furthermore,  advanced  methods  of  harvesting 
these  plants  have  made  it  possible  to  secure  three  or  four  harvestings 
in  one  season,  whereas  in  former  years  one  or  two  was  the  limit." 
The  experience  gained  by  the  author  in  the  production  of  cer- 
tain drug  plants  extending  over  the  past  three  years  confirms  the 
statements  of  the  experts  quoted  above.  The  fact  is  very  clearly 
brought  out  that  the  so-called  "  backyard "  movement,  however 
