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46  EFFECTS  OF  SOIL,  ETC.  ON  ACTIVE  PRINCIPLES  OF  PLANTS. 
equally  fitted  for  its  peculiar  habits,  can  hardly  be  considered 
as  cultivation. 
It  is,  however,  more  difficult  to  imitate  nature  on  such  a  point, 
than  to  supply  the  exact  pabulum  for  a  plant,  or  to  sustain 
those  conditions  under  which  a  plant  grows  in  a  wild  or  natural 
state. 
The  circumstances  which  I  proposed  to  consider,  as  affecting 
the  medicinal  value  of  a  plant,  are: — mutilation,  when  giving 
rise  to  an  unnatural  development  of  particular  parts  ;  effects  of 
soil,  as  indicated  by  the  chemical  analysis  of  the  soil  and  plant ; 
and  situation,  with  reference  to  the  supply  of  air,  light,  and 
moisture. 
The  principle  of  mutilation  is  not  generally  practised,  al- 
though by  suppressing  the  development  of  flowers,  a  larger 
number  of  leaves  may  be  obtained.  In  the  case  of  the  Labiatse, 
we  may,  by  suppressing  the  development  of  wood,  produce  a 
larger  quantity  of  oil,  but  it  does  not  appear  that  by  the  mere 
removal  of  leaves,  a  larger  quantity  of  oil  is  obtainable,  more 
flowers  are  developed,  but  the  yield  of  oil  is  proportionally  di- 
minished ;  this  might  possibly  admit  of  explanation,  from  the 
importance  of  the  functions  which  the  leaves  perform  in  regula- 
ting evaporation  and  supplying  air,  the  main  features  in  the 
elaboration  of  the  vegetable  fluids. 
Mutilation  will  not  in  every  case  account  for  the  non-develop- 
ment of  any  particular  organ  or  part  of  a  plant. 
I  planted  about  three  years  ago,  but  without  determining  the 
suitability  of  the  soil,  several  slips  of  rosemary  :  they  have  all 
put  out  abundance  of  shoots  and  leaves,  but  the  number  of 
flowers  has  been  very  insignificant ;  no  mutilation  has  ever 
taken  place.  At  the  same  time  I  laid  out  several  plants  of 
lavender,  which  became  completely  exhausted  after  the  second 
year,  and  out  of  forty  slips  planted  at  the  same  time,  not  one 
struck ;  this,  I  have  since  discovered,  may  be  explained  by  the 
chemical  condition  of  the  soil  (see  analysis  in  Appendix),  and 
the  physical  requirements  of  the.  plant. 
Non-mutilated  lavender  plants  yield  considerably  finer  flow- 
ers, when  grown  on  a  suitable  soil,  but  the  quantity  is  much 
less  than  from  plants  in  which  the  development  of  wood  is  pre- 
