400 
Insects  and  Flowers. 
Am.  Jour.  Pharm. 
Aug.,  1886. 
his  meaning  with  precision  in  some  introductory  remarks  to  his 
work  on  "Cross  and  Self-Fertilization."  These  are  his  words:  "In 
1862,1  summed  up  my  observations  on  orchids  by  saying  that  nature 
abhors  perpetual  self-fertilization;  if  the  word  perpetual  had  been 
omitted,  the  aphorism  would  have  been  false."  And  in  another 
place:  "  From  my  own  observations  on  plants  I  became  convinced, 
many  years  ago,  that  it  is  a  general  law  of  nature  that  flowers  are 
adapted  to  be  crossed,  at  least  occasionally,  by  pollen  from  a  distinct 
plant."  This  opinion  was  ratified  by  Andrew  Knight  in  these 
words:  "In  no  plant  does  self-fertilization  occur  for  an  unlimited 
number  of  generations." 
It  will  be  remarked  how  wide  a  difference  exists  between  the 
guarded  expressions  of  these  careful  inquirers  and  the  rash  law-giving 
of  later  writers,  who,  although  working  on  the  lines  laid  down  by 
Darwin,  have  assuredly  studied  only  the  contrivances  which  are 
favorable  to  cross-fertilization,  and  neglect  to  make  mention  of  those 
facts,  so  weighty  and  so  numerous,  which  tell  so  dead  against  them. 
They  appear  to  forget  that  there  are  many  plants  whose  pollen  is 
wafted  away  by  the  wind,  and  which  are  wholly  independent  of  in- 
sects. That  there  are  great  numbers  which  are  propagated  by 
grafts,  buds,  layers,  bulbs,  tubers,  and  cuttings,  besides  over  thirty 
natural  orders  of  cleistogamic  plants,  closed  to  all  comers,  necessarily 
self-fertilized. 
In  1869  Severin  Axell  divested  some  hasty  conceptions  of  their 
one-sidedness,  and,  besides  the  facts  just  mentioned,  he  drew  out  a 
list  of  plants  in  which  self-fertilization  inevitably  takes  place,  men- 
tioning those  also  which  are  aquatic,  and  which,  under  ordinary 
circumstances,  expand  their  flowers  at  the  surface  of  the  water,  and 
are  cross-fertilized  by  the  wind,  but  which  remain  closed  when  the 
water  is  unusually  high,  and  then  fertilize  themselves,  producing 
seeds  which  propagate  the  species. 
Even  the  history  of  the  orchids,  that  stronghold  of  insect  agency, 
tends,  from  recent  observations,  to  show  that  intercrossing  is  not  so 
advantageous  as  it  is  supposed  to  be,  since  many  tropical  kinds, 
cited  as  especially  adapted  for  intercrossing,  are  found  to  an  enor- 
mous extent  utterly  barren,  whilst  several  species  which  exhibit  re- 
markable adaptations  for  close  fertilization  produce  abundance  of  seed. 
This  would  appear  a  startling  contradiction  to  Darwin,  until  it  is 
recollected  that,  with  his  usual  candor,  he  points  out  the  sterility  of 
