﻿524 
  Mutations 
  

  

  branches. 
  Most 
  of 
  them 
  are 
  crowned 
  with 
  

   flowers 
  in 
  summer, 
  which 
  regularly 
  succeed 
  each 
  

   other, 
  leaving 
  behind 
  them 
  long 
  spikes 
  of 
  young 
  

   fruits. 
  The 
  flowers 
  are 
  large 
  and 
  of 
  a 
  bright 
  

   yellow 
  color, 
  attracting 
  immediate 
  attention, 
  

   even 
  from 
  a 
  distance. 
  They 
  open 
  towards 
  

   evening, 
  as 
  the 
  name 
  indicates, 
  and 
  are 
  pollin- 
  

   ated 
  by 
  humble-bees 
  and 
  moths. 
  On 
  bright 
  days 
  

   their 
  duration 
  is 
  confined 
  to 
  one 
  evening, 
  but 
  

   during 
  cloudy 
  weather 
  they 
  may 
  still 
  be 
  found 
  

   open 
  on 
  the 
  following 
  morning. 
  Contrary 
  to 
  

   their 
  congeners 
  they 
  are 
  dependent 
  on 
  visiting 
  

   insects 
  for 
  pollination. 
  0. 
  biennis 
  and 
  0. 
  

   muricata 
  have 
  their 
  stigmas 
  in 
  immediate 
  con- 
  

   tact 
  with 
  the 
  anthers 
  within 
  the 
  flower-buds, 
  and 
  

   as 
  the 
  anthers 
  open 
  in 
  the 
  morning 
  preceding 
  

   the 
  evening 
  of 
  the 
  display 
  of 
  the 
  petals, 
  fecun- 
  

   dation 
  is 
  usually 
  accomplished 
  before 
  the 
  in- 
  

   sects 
  are 
  let 
  in. 
  But 
  in 
  0. 
  lamarckiana 
  no 
  

   such 
  self-fertilization 
  takes 
  place. 
  The 
  stigmas 
  

   are 
  above 
  the 
  anthers 
  in 
  the 
  bud, 
  and 
  as 
  the 
  

   style 
  increases 
  in 
  length 
  at 
  the 
  time 
  of 
  the 
  

   opening 
  of 
  the 
  corolla, 
  they 
  are 
  elevated 
  above 
  

   the 
  anthers 
  and 
  do 
  not 
  receive 
  the 
  pollen. 
  Or- 
  

   dinarily 
  the 
  flowers 
  remained 
  sterile 
  if 
  not 
  vis- 
  

   ited 
  by 
  insects 
  or 
  pollinated 
  by 
  myself, 
  although 
  

   rare 
  instances 
  of 
  self-fertilization 
  were 
  seen. 
  

  

  In 
  falling 
  off, 
  the 
  flowers 
  leave 
  behind 
  them 
  

   a 
  stout 
  ovary 
  with 
  four 
  cells 
  and 
  a 
  large 
  number 
  

  

  