﻿POLLINATION 
  AND 
  FERTILIZATION 
  137 
  

  

  and, 
  together 
  with 
  the 
  embryo, 
  they 
  constitute 
  the 
  seed. 
  Under 
  

   favorable 
  circumstances 
  the 
  seed 
  may 
  germinate 
  and 
  the 
  em- 
  

   bryo 
  grow 
  into 
  an 
  adult 
  plant. 
  One 
  pollen 
  grain 
  may 
  suffice 
  

   to 
  fertilize 
  an 
  ovule, 
  but 
  the 
  result 
  is 
  more 
  certain 
  if 
  there 
  are 
  

   several 
  germinating 
  pollen 
  grains 
  for 
  each 
  ovule, 
  though 
  but 
  

   one 
  male 
  cell 
  unites 
  with 
  one 
  egg. 
  

  

  oo 
  

  

  128. 
  Pollination 
  an 
  ecological 
  subject. 
  Before 
  considering 
  

   the 
  ecology 
  of 
  flowers 
  it 
  is 
  necessary 
  to 
  explain 
  what 
  is 
  meant 
  

   by 
  plant 
  ecology. 
  It 
  is 
  impossible 
  to 
  study 
  plants 
  in 
  any 
  all- 
  

   round 
  fashion 
  without 
  paying 
  a 
  good 
  deal 
  of 
  attention 
  to 
  the 
  

   way 
  in 
  which 
  they 
  are 
  influenced 
  by 
  their 
  surroundings. 
  Any 
  

   change 
  in 
  the 
  temperature, 
  light, 
  water 
  supply, 
  or 
  supply 
  of 
  

   raw 
  materials 
  for 
  food-making 
  is 
  sure 
  to 
  affect 
  the 
  plant 
  in 
  

   some 
  way. 
  Hillside, 
  plain, 
  swamp, 
  lake, 
  or 
  sea 
  each 
  has 
  its 
  

   own 
  flora, 
  or 
  set 
  of 
  plant 
  inhabitants, 
  which 
  can 
  thrive 
  under 
  

   the 
  conditions 
  found 
  in 
  their 
  growing 
  place. 
  Plants 
  are 
  also 
  

   greatly 
  affected 
  by 
  the 
  favorable 
  or 
  unfavorable 
  influences 
  

   exerted 
  on 
  them 
  by 
  their 
  animal 
  and 
  plant 
  neighbors. 
  The 
  

   whole 
  subject 
  of 
  the 
  relation 
  of 
  plants 
  to 
  the 
  environment 
  in 
  wht'i-h 
  

   tliey 
  live 
  is 
  known 
  as 
  plant 
  ecoloai/. 
  In 
  earlier 
  chapters 
  much 
  

   has 
  been 
  stated, 
  and 
  still 
  more 
  suggested, 
  that 
  concerns 
  this 
  

   side 
  of 
  botany, 
  but 
  the 
  subject 
  was 
  not 
  treated 
  in 
  detail, 
  because 
  

   it 
  is 
  one 
  of 
  the 
  most 
  difficult 
  departments 
  of 
  botanical 
  science 
  

   and 
  its 
  study 
  is 
  as 
  yet 
  only 
  fairly 
  begun. 
  In 
  this 
  chapter 
  most 
  

   that 
  is 
  to 
  be 
  said 
  of 
  the 
  processes 
  of 
  pollination 
  should 
  be 
  

   classed 
  as 
  pertaining 
  to 
  the 
  ecology 
  of 
  flowers. 
  

  

  129. 
  Relation 
  of 
  types 
  of 
  floral 
  structure 
  to 
  pollination. 
  

   Probably 
  most 
  students 
  of 
  plants, 
  from 
  the 
  earliest 
  times, 
  

   were 
  somewhat 
  puzzled 
  over 
  the 
  great 
  variety 
  in 
  form, 
  colora- 
  

   tion, 
  odor, 
  and 
  other 
  characteristics 
  shown 
  by 
  flowers, 
  but 
  until 
  

   about 
  a 
  hundred 
  and 
  fifty 
  years 
  ago 
  no 
  botanist 
  seems 
  even 
  to 
  

   have 
  reasoned 
  about 
  the 
  facts 
  that 
  some 
  flowers 
  are 
  over 
  a 
  

   yard 
  in 
  diameter, 
  while 
  others 
  are 
  almost 
  microscopic 
  ; 
  that 
  

   some 
  spread 
  the 
  perianth 
  widely 
  and 
  others 
  are 
  narrowly 
  

   tubular 
  or 
  urn-shaped 
  ; 
  that 
  some 
  are 
  sweet-scented, 
  others 
  

   carrion-scented, 
  and 
  others 
  odorless 
  ; 
  that 
  some 
  have 
  extremely 
  

  

  