348 
Charles  Darwin. 
Am.  Jour.  Pharm. 
July,  1909. 
The  advances  that  have  been  made  by  the  assistance  of  many  work- 
ers have  necessitated  a  restatement  of  all  of  the  most  important 
doctrines  which  Darwin  enunciated.  Take,  for  example,  the  empha- 
sis which  he  laid  upon  the  principle  that  Nature  abhors  continuous 
self-fertilization.  He  has  given  us  by  his  experiments  narrated  in 
"  Cross  and  Self-Fertilization  in  the  Vegetable  Kingdom "  some 
accurate  data  tending  to  show  the  actual  effect  of  inbreeding  for  a 
great  variety  of  species.  His  experiments  were  with  some  57  species, 
belonging  to  52  genera.  One  of  his  most  extensive  series  of  experi- 
ments was  carried  on  with  the  common  morning  glory  (Ipomcea 
purpurea).  This  species  was  bred,  both  crossed  and  self-fertilized, 
for  ten  generations.  In  every  generation,  the  crossed  forms  were 
larger  than  the  self-fertilized,  the  average  being  as  100  is  to  77. 
Not  only  that,  but  they  were  more  productive.  In  the  sixth  genera- 
tion, however,  there  appeared  a  specially  vigorous  plant  that  over- 
topped its  own  competitor  by  half  an  inch,  and  exceeded  in  height 
all  but  three  of  the  series.  Darwin  named  this  plant  "  Hero  "  and 
remarks,  "  I  was  so  much  surprised  at  this  fact  that  I  resolved  to 
ascertain  whether  this  plant  would  transmit  its  powers  of  growth 
to  its  seedlings."  Accordingly,  he  fertilized  a  number  of  flowers 
of  Hero  with  their  own  pollen  and  planted  seedlings  in  competition 
with  inbred  plants  and  with  the  cross-bred  as  well.  The  results 
obtained  showed  that  Hero  and  its  descendants  varied  from  the 
common  type  not  only  in  acquiring  great  power  of  growth  and 
increased  fertility,  when  subjected  to  self-fertilization,  but  in  not 
profiting  from  a  cross  with  distinct  stock.  Although  Darwin  was 
surprised  at  Hero  and  its  descendants,  yet  he  mentioned  the  case 
as  obviously  contrary  to  the  usual  procedure  among  plants.  We 
now  know,  however,  that  there  are  many  hundreds  of  plants  which 
possess  cleistogamous  flowers,  which  are  habitually  self-pollinated 
without  any  apparent  diminution  in  vigor  or  hardiness,  as,  for 
example,  our  common  blue  violet  which  produces  seed  more  abun- 
dantly underground  from  cleistogamous  flowers  than  from  the 
bright  blue  flowers  which  are  one  of  the  glories  of  our  hillsides  in 
the  early  springtime.  The  same  general  exception  has  been  proved 
in  animal  breeding,  where  line  breeding  has  been  found  one  of  the 
most  powerful  methods  of  improving  the  race  of  our  common 
domestic  animals,  and  that  inbreeding  of  the  most  pronounced  kind 
is  not  always  detrimental  provided  the  breeder  selects  the  animals 
to  be  bred  with  reference  to  their  vigor  and  fertility. 
