﻿CHAPTER 
  X 
  

  

  POLLINATION 
  AND 
  FERTILIZATION 
  

  

  124. 
  Pollination. 
  In 
  the 
  great 
  majority 
  of 
  flowering 
  plants 
  

   seed 
  production 
  depends 
  indirectly 
  upon 
  pollen. 
  Of 
  course 
  the 
  

   pollen 
  grain, 
  in 
  order 
  to 
  act, 
  must 
  be 
  t 
  ranst'envd 
  from 
  the 
  anther, 
  

   where 
  it 
  was 
  formed, 
  to 
  the 
  pistil, 
  in 
  which 
  are 
  the 
  ovules 
  to 
  

  

  be 
  affected. 
  This 
  transference 
  of 
  

   pollen 
  is 
  called 
  pollination. 
  

  

  In 
  the 
  higher 
  seed 
  plants 
  the 
  

   pollen 
  is 
  received 
  on 
  the 
  surface 
  of 
  

   the 
  stigma, 
  which 
  is 
  usually 
  rough, 
  

   moist, 
  and 
  sticky, 
  and 
  therefore 
  

   readily 
  retains 
  the 
  grains 
  which 
  

   reach 
  its 
  surface. 
  The 
  details 
  of 
  

   the 
  pollinating 
  process 
  differ 
  so 
  

   much 
  in 
  different 
  kinds 
  of 
  flowers 
  

   that 
  even 
  a 
  mere 
  statement 
  of 
  the 
  

   various 
  types 
  requires 
  considerable 
  

   space. 
  The 
  significance 
  of 
  pollina- 
  

   tion 
  will 
  appear 
  more 
  clearly 
  if 
  

   we 
  first 
  give 
  a 
  very 
  brief 
  account 
  

   of 
  the 
  results 
  of 
  pollination, 
  and 
  

   then 
  consider 
  a 
  few 
  of 
  the 
  modes 
  

   of 
  transference 
  of 
  pollen. 
  

  

  125. 
  Pollen 
  grains 
  ; 
  formation 
  of 
  pollen 
  tubes. 
  The 
  form 
  of 
  

   pollen 
  grain 
  for 
  any 
  given 
  kind 
  of 
  llo\ver, 
  as 
  a 
  lily, 
  a 
  hollyhock, 
  

   or 
  a 
  cucumber 
  blossom, 
  is 
  quite 
  constant, 
  but 
  those 
  of 
  differ- 
  

   ent 
  kinds 
  are 
  so 
  often 
  unlike 
  that 
  the 
  whole 
  number 
  of 
  forms 
  

   observed 
  is 
  very 
  great. 
  Usually 
  the 
  grains 
  are 
  separate, 
  like 
  

   those 
  shown 
  in 
  figure 
  117, 
  but 
  in 
  many 
  kinds 
  they 
  are 
  united 
  by 
  

  

  134 
  

  

  FIG. 
  117. 
  Types 
  of 
  pollen 
  grains 
  

  

  A, 
  dandi-lion 
  ; 
  U, 
  hemp 
  ; 
  C, 
  gen- 
  

   tian; 
  />, 
  squash. 
  All 
  greatly 
  

   m;i 
  i;nili 
  nl. 
  At'lrr 
  

  

  