Am.  Jour.  Pharm. 
Aug.,  1886. 
Insects  and  Flowers. 
401 
many  English  orchids,  and  remarks  that  the  bee  ophrys  is  excel- 
lently constructed  for  self-fertilization,  and  that  the  fly  and  spider 
orchis  are  never  visited  by  insects. 
It  is  known  that  a  great  number  of  alpine  plants  grow  beyond 
the  height  at  which  they  can  produce  seed,  and  those  growing  on 
mountain  pastures  generally  propagate  themselves  by  bulblets.  Many 
of  our  own  very  common  plants  do  not  set  seed.  The  horseradish 
never  produces  any.  The  periwinkle  spreads  largely  by  runners. 
The  varieties  of  peas  keep  true  because  they  are  not  ciossed  by  in- 
sects. The  St.  John's  wort  rarely  sets  seed.  Poppies  produce  plenty 
of  capsules  when  insects  are  excluded. 
An  argument,  which  may  be  used  either  way,  is  adduced  by 
Darwin,  whilst  insisting  on  the  greater  size  and  vigor  of  the  offspring 
of  crossed  flowers.  "It  might  have  been  expected,''  he  says,  "that 
the  seedlings  from  plants,  the  flowers  of  which  were  excessively 
sterile,  would  have  profited  in  a  greater  degree  by  a  cross  than  the 
seedlings  from  plants  which  were  moderately  or  fully  self-fertile, 
and,  therefore,  had  no  need  to  be  crossed ;  but  no  such  results  fol- 
lowed." He  also  admits  that  there  are  no  signs  of  degeneracy  in  the 
bee  or  other  self-fertilized  orchids,  and  that  they  are  all  vigorous 
growers. 
The  assertion  that  brilliant  hues  and  full  cups  are  designed  as 
allurements  to  insects  is  abundantly  contradicted  by  foreign  botan- 
ists, who  describe  plants  with  conspicuously  beautiful  flowers,  which 
are  as  much  adapted  to  secure  self-fertilization  as  others  are  for  cross- 
ing, and  many  of  our  own  native  flowers,  secreting  much  nectar  and 
producing  much  pollen,  are  wholly  disregarded  by  butterflies,  flies, 
and  bees. 
That  color  variation  is  wholly  attributable  to  insects  is  exceedingly 
doubtful,  and  that  all  the  brilliant  colors  descended  from  the  primeval 
yellow  are  due  to  their  selective  agency  is  so  evidently  a  fallacious 
doctrine  that  very  few  words  will  be  required  to  refute  it.  The 
doctrine  is  this:  that  the  colors  of  flowers  are  intended  to  attract 
insects,  and  that  certain  colors  are  definitely  intended  to  attract  cer- 
tain kinds  of  insects. 
That  flowers  which  lay  themselves  open  for  fertilization  by  miscel- 
laneous small  flies  are  white;  those  which  depend  on  beetles  are  yel- 
low. Butterflies  prefer  red,  lilac  or  blue;  and  bees  blue;  blue  flowers 
being,  as  a  rule,  specialized  for  fertilization  by  bees. 
