BE.  HOOKER'S  ADDRESS  TO  THE  BRITISH  ASSOCIATION.  561 
stigma,  but  invariably  potent  when  applied  to  the  stigma  of  the 
other  form  of  flower  ;  and  yet  both  pollens  and  stigmas  of  the 
two  kinds  are  utterly  un  distinguishable  under  the  highest  powers 
of  the  microscope. 
His  third  investigation  is  a  very  long  and  laborious  one  on 
the  common  loose-strife,*  (Lythrum  salicaria),  which  he  showed 
to  be  trimorphic,  this  one  species  having  three  kinds  of  flowers, 
all  annually  abundantly  produced,  and  as  different  as  if  they  be- 
longed to  different  species  ;  each  flower  has,  further,  three  kinds 
of  stamens,  differing  in  form  and  function.  We  have  in  this 
plant,  then,  six  kinds  of  pollen,  of  which  five  at  least  are  essen- 
tial to  complete  fertility,  and  three  distinct  forms  of  style.  To 
prove  these  various  differences,  and  that  the  co-adaptation  of  all 
these  stamens  and  pistils  was  essential  to  complete  fertility,  Mr. 
Darwin  had  to  institute  eighteen  sets  of  observations,  each  con- 
sisting of  twelve  experiments,  216  in  all.  Of  the  labor,  care  and 
delicacy  required  to  guard  such  experiments  against  the  possi- 
bility of  error,  those  alone  can  tell  who  know  experimentally 
how  difficult  it  is  to  hybridize  a  large  flowered  plant  of  simple 
form  and  structure.  The  results  in  this  case,  and  in  those  of  a 
number  of  allied  plants  experimented  on  at  the  same  time,  is 
what  the  author's  sagacity  predicted  ;  the  rationale  of  the  whole 
was  demonstrated,  and  he  finally  showed,  not  only  how  nature 
might  operate  in  bringing  these  complicated  modifications  into 
harmonious  operation,  but  how  through  insect  agency  she  does 
do  this,  and  why  she  does  it  too. 
It  is  impossible  even  to  enumerate  here  the  many  important 
generalizations  that  have  flowed  from  these  and  other  papers  of 
Mr.  Darwin's  on  the  fertilization  of  plants  ;  some  that  appear  to 
be  common-place  at  first  are  really  the  most  subtle,  and,  like 
many  other  apparent  common-places,  are  what,  somehow,  never 
occur  to  common-place  minds :  as,  for  instance,  that  all  plants 
with  conspicuously  colored  flowers,  or  powerful  odors,  or  honeyed 
secretions,  are  fertilized  by  insects ;  all  with  inconspicuous  flowers, 
and  especially  such  as  have  pendulous  anthers,  or  incoherent 
pollen,  are  fertilized  by  the  wind  ;  from  whence  he  infers  that, 
*  Linnean  Transactions.,  vol.  viii,  p.  169. 
37 
