﻿152 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  it 
  seems 
  probable 
  that 
  the 
  colors 
  of 
  flowers 
  are 
  an 
  important 
  

   means 
  of 
  attraction 
  for 
  many 
  flower-frequenting 
  insects. 
  1 
  

  

  Tin- 
  commonest 
  method 
  of 
  color 
  display 
  is 
  that 
  in 
  which 
  

   the 
  color 
  (other 
  than 
  green) 
  is 
  mainly 
  found 
  in 
  the 
  corolla, 
  

   as 
  in 
  the 
  flowers 
  of 
  the 
  poppy, 
  rose, 
  sweet 
  pea, 
  and 
  morning- 
  

   glory. 
  Sometimes 
  the 
  calyx 
  also 
  is 
  bright-colored, 
  or, 
  as 
  in 
  

  

  t 
  he 
  Hepatica, 
  the 
  Anemone, 
  and 
  

   the 
  ( 
  'IciiKitix, 
  the 
  corolla 
  is 
  want- 
  

   ing 
  and 
  the 
  showy 
  calyx 
  looks 
  

   1 
  ike 
  a 
  corolla. 
  Not 
  infrequently 
  

   the 
  display 
  is 
  all 
  made 
  by 
  an 
  

   enlarged 
  and 
  conspicuous 
  set 
  of 
  

   specialized 
  leaves 
  (bracts') 
  sur- 
  

   rounding 
  the 
  flower, 
  as 
  in 
  the 
  

   flowering 
  dogwood 
  and 
  many 
  

   euphorbias 
  (fig. 
  67), 
  or 
  even 
  by 
  

   highly 
  colored 
  ordinary 
  leaves, 
  

   like 
  those 
  of 
  the 
  poinsettia. 
  

  

  144. 
  Prevention 
  of 
  self-polli- 
  

   nation 
  ; 
  dichogamy. 
  Of 
  course, 
  

   dio-cioiis 
  flowers, 
  like 
  those 
  

   of 
  the 
  willow, 
  cannot 
  be 
  self- 
  

   pollinated. 
  In 
  the 
  culture 
  of 
  

   not 
  yet 
  appearing 
  outside 
  the 
  corolla; 
  date 
  palms 
  it 
  is 
  usual 
  to 
  polli- 
  

  

  />', 
  later 
  stum', 
  pistil 
  \vitlicrcil, 
  stiimens 
  . 
  . 
  n 
  a 
  \ 
  

  

  matim.. 
  six 
  <im,s 
  natural 
  size 
  mite 
  tlie 
  pistillate 
  flowers 
  by 
  

  

  hand, 
  Momecious 
  flowers, 
  like 
  

  

  those 
  of 
  Indian 
  corn 
  (figs. 
  126 
  and 
  127) 
  are 
  likely 
  to 
  be 
  pol- 
  

   linated 
  with 
  pollen 
  from 
  another 
  plant, 
  As 
  regards 
  bisexual 
  

   flowers, 
  it 
  is 
  evident 
  that 
  there 
  are 
  many 
  opportunities 
  for 
  self- 
  

   pollination 
  ; 
  but 
  in 
  all 
  cases 
  in 
  which 
  cross-pollinat 
  ion 
  produces 
  

   more 
  seed 
  or 
  stronger 
  plants, 
  or 
  both, 
  it 
  is 
  clear 
  that 
  anything 
  

   in 
  the 
  structure 
  or 
  mode 
  of 
  development 
  of 
  the 
  flower 
  which 
  

   tends 
  to 
  secure 
  cross-pollination 
  is 
  highly 
  advantageous. 
  One 
  

  

  1 
  Srr 
  Krriirr 
  -< 
  Hiv.T, 
  Natural 
  History 
  of 
  Plants. 
  Vol. 
  IT. 
  Henry 
  Holt 
  and 
  

   Company, 
  New 
  York. 
  Also 
  Knnth-Davis, 
  Handbook 
  of 
  Flower 
  Pollination, 
  

   Vol. 
  I. 
  

  

  A 
  B 
  

  

  Fa;. 
  130. 
  Dichogamous 
  flowers 
  of 
  

   plantain 
  (Plantago 
  lanccolata) 
  

  

  A, 
  earlier 
  stage, 
  pistil 
  mature, 
  stamens 
  

  

  