﻿POLLINATION 
  AND 
  FERTILIZATION 
  

  

  145 
  

  

  FIG. 
  128. 
  Flower 
  of 
  

  

  potato, 
  with 
  widely 
  

  

  expanded 
  corolla 
  

  

  138. 
  The 
  periwinkle 
  ; 
  a 
  flower 
  with 
  concealed 
  nectar. 
  The 
  

   common 
  periwinkle, 
  1 
  a 
  familiar 
  old-fashioned 
  flower, 
  is 
  an 
  ex- 
  

   cellent 
  illustration 
  of 
  one 
  way 
  in 
  which 
  nectar 
  is 
  concealed 
  

   and 
  protected 
  from 
  undesirable 
  insect 
  visi- 
  

   tors. 
  The 
  tube 
  of 
  the 
  corolla 
  is 
  moderately 
  

   long 
  and 
  is 
  partly 
  closed 
  by 
  a 
  sort 
  of 
  disk- 
  

   shaped 
  enlargement 
  of 
  the 
  style 
  (fig. 
  129). 
  

   Part 
  of 
  the 
  under 
  surface 
  of 
  the 
  disk 
  does 
  

   the 
  work 
  of 
  a 
  stigma. 
  

  

  The 
  disk 
  is 
  surrounded 
  by 
  gummy 
  mate- 
  

   rial 
  and 
  bears 
  a 
  crown 
  of 
  hairs 
  at 
  the 
  top. 
  

   The 
  anthers 
  open 
  inward 
  and 
  so 
  fill 
  the 
  crown 
  of 
  hairs 
  with 
  

   pollen. 
  The 
  long, 
  slender 
  tongue 
  of 
  an 
  insect 
  visitor 
  (fig. 
  130), 
  

   in 
  being 
  thrust 
  through 
  the 
  fringing 
  hairs 
  and 
  down 
  the 
  tube 
  

   in 
  search 
  of 
  nectar 
  at 
  its 
  base, 
  becomes 
  covered 
  with 
  pollen. 
  

   In 
  this 
  way 
  some 
  of 
  it 
  will 
  be 
  

   left 
  on 
  the 
  stigma 
  of 
  the 
  next 
  

   periwinkle 
  flower 
  visited, 
  which 
  

   will 
  secure 
  cross-fertilization. 
  

  

  Many 
  other 
  instances 
  of 
  con- 
  

   cealment 
  of 
  the 
  nectar 
  supply 
  

   can 
  be 
  discovered 
  by 
  the 
  observ- 
  

   ing 
  student. 
  One 
  of 
  the 
  most 
  

   obvious 
  is 
  in 
  such 
  flowers 
  as 
  

  

  snapdragon 
  and 
  butter-and-eggs, 
  

  

  1 
  . 
  . 
  " 
  ,. 
  , 
  FIG. 
  129. 
  Lengthwise 
  section 
  of 
  

  

  in 
  which 
  the 
  two-lipped 
  corolla 
  flower 
  of 
  periwinkle 
  (Finca 
  minor), 
  

  

  is 
  rather 
  firmly 
  closed, 
  SO 
  that 
  the 
  corolla 
  with 
  a 
  closed 
  throat 
  and 
  

  

  it 
  can 
  only 
  be 
  pried 
  open 
  by 
  a 
  witn 
  the 
  nectar 
  not 
  accessible 
  to 
  

  

  most 
  small 
  insects 
  

   moderately 
  strong 
  insect. 
  

  

  There 
  is 
  a 
  large 
  class 
  of 
  

  

  s, 
  disk-shaped 
  expansion 
  of 
  the 
  style, 
  

   stigmatic 
  on 
  its 
  lower 
  surface 
  ; 
  n, 
  nec- 
  

   tar 
  glands 
  at 
  the 
  base 
  of 
  the 
  ovary 
  

  

  is 
  a 
  large 
  

  

  flowers 
  in 
  which 
  the 
  nectar 
  is 
  

   not 
  so 
  much 
  concealed 
  as 
  out 
  

  

  of 
  the 
  reach 
  of 
  ordinary 
  insects, 
  since 
  it 
  is 
  at 
  the 
  bottom 
  of 
  

   a 
  long 
  and 
  narrow 
  corolla 
  tube 
  or 
  in 
  a 
  slender 
  spur 
  of 
  the 
  

   corolla. 
  Excellent 
  instances 
  of 
  this 
  are 
  found 
  in 
  the 
  flowers 
  

  

  minor. 
  

  

  