48  EFFECTS  OF  SOIL,  ETC.  ON  ACTIVE  PRINCIPLES  OF  PLANTS. 
after  flowering;  it  is  slightly  diminished  in  the  stalks  and  roots 
after  the  fall  of  the  flower,  and  gradually  accumulates  in  the  re- 
maining appendages  of  the  flower. 
The  maximum  accumulation  in  the  seeds  and  seed-vessels  of 
foxglove  and  stramonium,  I  have  found  to  be  attained  before 
the  seeds  change  their  color. 
In  the  case  of  belladonna,  this  is  not  so  strongly  marked  as 
in  foxglove,  henbane,  or  stramonium. 
With  good  specimens  of  foxglove  recently  collected,  it  is  easy 
to  obtain  the  color  reaction  of  digitaline,  by  simply  moistening 
the  seeds  with  dilute  sulphuric  acid. 
These  experiments  have  been  confined  entirely  to  the  bien- 
nials, in  some  cases  transplanted  so  as  to  be  within  easy  access. 
Although  I  have  closely  studied  the  effects  produced  by  cul- 
tivation, and  have  prepared  several  artificial  soils  to  determine 
the  effects  produced  by  differences  of  mineralizing  ingredients, 
I  regret  that  the  information  which  may  be  deduced  from  my 
experiments  is  so  limited.  This  is  necessitated  by  the  fact,  that 
it  is  not  easy  to  detect  any  differences  in  the  mineral  composi- 
tion of  the  juices  of  a  plant,  which  may  be  raised  on  soils  having 
a  slight  difference  in  their  mineral  constituents  ;  and  since  time 
is  required  for  the  indication  of  a  maximum  effect  on  the  chemi- 
cal constitution  of  a  plant,  and  the  degree  of  acceleration  with 
which  such  effect  is  produced,  and  as  my  experiments  have  been 
limited  to  a  single  year,  it  is  not  right  to  infer  that  the  results 
indicated  form  the  totality  of  what  might  under  the  continua- 
tion of  the  experiment  be  expected. 
There  can  be  no  doubt  that  the  continual  raising  of  medici- 
nal crops  upon  any  soil,  without  supplying  the  same  with  ma- 
nure in  some  form,  must  be  followed  by  an  alteration  in  the 
chemical  constituents  of  the  plants ;  such  effects  can  be  deter- 
mined only  by  experiments  extending  over  three  or  four  years. 
From  the  information  which  I  have  been  able  to  gather,  it  is 
quite  probable  that  the  careful  application  of  manure  to  medici- 
nal crops  is  of  essential  importance,  and  that  merely  restoring 
the  saline  matter  to  tbe  soil  which  had  been  extracted  during 
vegetation  will  not  maintain  its  productive  capacity. 
Most  growers  with  whom  I  am  acquainted  adopt  the  princi- 
