EFFECTS  OF  SOIL,  ETC.  ON  ACTIVE  PRINCIPLES  OF  PLANTS.  53 
ers  compensate  for  such  plants  which  require  a  more  exposed 
position  than  can  be  obtained  in  the  general  way  of  cultivation. 
The  tendency  which  some  growers  have  of  planting  closely 
may  explain  the  differences  which  have  been  observed  in  the 
medicinal  effects  of  some  plants,  as  foxglove  and  henbane.  It 
is  highly  probable  that  growers  have  been  stimulated  to  this 
practice  by  competitive  impulse. 
It  is  well  known  that  plants  which  are  secluded  from  light 
cannot  perfect  their  seeds,  nor  effect  the  deoxidation  of  carbonic 
acid.  As  this  results  where  the  plants  are  situated  closely  to 
each  other,  especially  if  they  have  large  leaves,  it  is  highly  pro- 
bable that  species  may  be  produced.  This  may  serve  to  ex. 
plain  the  singular  effect  which  I  have  already  noticed  in  refer- 
ence to  henbane. 
Appendix* 
A.  Analysis  of  Soil  from  a  Wood  near  Wimbledon. 
Chlorides,  magnesium  and  potassium     .       .  2*1 
Sulphate  of  lime    .       .       .       .       .       .  *3 
Carbonate  of  lime         .....  3*5 
Carbonate  of  magnesia          .       .       .       .  1*1 
Oxide  of  iron  and  silica        .       .       .       .  2*0 
Water  (lost  at  212°)   12*0 
Organic  matter      ......  73*0 
Loss      ........  6*0 
100-0 
B.  Analysis  of  Soil ;  vide  page  213. 
Phosphate  of  lime,  with  traces  of  magnesia    .  9-0 
Chloride  of  potassium  and  sodium        .       .  4*6 
Sulphate  of  lime    ......  '5 
Nitrate  and  phosphate  of  ammonia        .       .  *7 
Silica     .       .       ._      .....  9*1 
Oxide  of  iron        .       .       .       .-             .  1*1 
Organic  matter    , ,       .       .       .       .       .  63*3 
Water    ........  8-0 
Loss      ........  3-7 
100-0 
