﻿POODS 
  IN 
  PLANTS 
  37 
  

  

  35. 
  Chlorophyll 
  in 
  the 
  leaf. 
  The 
  so-called 
  green 
  cells 
  of 
  the 
  

   leaf 
  are 
  not 
  evenly 
  green 
  throughout, 
  but 
  contain 
  special 
  

   bodies 
  (plasts, 
  or 
  plastids) 
  in 
  which 
  the 
  chlorophyll 
  is 
  held. 
  

   These 
  chlorophyll-bearing 
  bodies, 
  or 
  chloroplasts, 
  are 
  often 
  so 
  

   numerous 
  in 
  the 
  cells 
  of 
  the 
  leaf 
  as 
  to 
  make 
  the 
  cell 
  appear 
  to 
  

   be 
  almost 
  of 
  a 
  solid 
  green 
  color, 
  and 
  when 
  the 
  surface 
  of 
  the 
  

   leaf 
  is 
  observed, 
  its 
  appearance 
  seems 
  evenly 
  green 
  throughout. 
  

  

  It 
  must 
  be 
  clearly 
  understood 
  that 
  chlorophyll 
  and 
  the 
  

   chloroplast 
  are 
  not 
  the 
  same. 
  Plastids 
  (plasts) 
  may 
  or 
  may 
  

   not 
  contain 
  chlorophyll, 
  just 
  as 
  a 
  sponge 
  may 
  or 
  may 
  not 
  con- 
  

   tain 
  water. 
  A 
  plastid 
  can 
  properly 
  be 
  called 
  a 
  chloroplast 
  only 
  

   when 
  it 
  contains 
  chlorophyll. 
  When 
  green 
  leaves 
  have 
  stood 
  

   in 
  alcohol 
  for 
  a 
  few 
  hours, 
  the 
  chlorophyll 
  is 
  dissolved 
  by 
  the 
  

   alcohol, 
  the 
  leaf 
  is 
  decolored, 
  and 
  the 
  color 
  of 
  chlorophyll 
  may 
  

   readily 
  be 
  observed 
  in 
  the 
  alcohol. 
  

  

  In 
  summing 
  up 
  the 
  structures 
  of 
  the 
  leaf 
  we 
  may 
  say 
  that 
  

   it 
  usually 
  consists 
  of 
  petiole 
  and 
  blade. 
  The 
  outer 
  portions 
  

   of 
  the 
  blade, 
  both 
  above 
  and 
  below, 
  are 
  the 
  epidermis 
  ; 
  in 
  ad- 
  

   dition 
  to 
  the 
  ordinary 
  epidermal 
  cells 
  the 
  epidermis 
  contains 
  

   special 
  structures, 
  the 
  stomata, 
  each 
  of 
  which 
  ordinarily 
  con- 
  

   sists 
  of 
  two 
  guard 
  cells 
  and 
  a 
  stomatal 
  cavity 
  ; 
  within 
  the 
  

   epidermis 
  are 
  the 
  veins 
  and 
  the 
  masses 
  of 
  green 
  tissue 
  --the 
  

   palisade 
  and 
  spongy 
  tissues; 
  within 
  the 
  cells 
  of 
  the 
  green 
  

   tissues, 
  in 
  addition 
  to 
  other 
  cell 
  contents, 
  are 
  many 
  plastids. 
  

   These 
  may 
  contain 
  chlorophyll 
  ; 
  they 
  are 
  then 
  known 
  as 
  

   ehloroplasts. 
  

  

  36. 
  Material 
  for 
  chlorophyll 
  work. 
  In 
  the 
  discussion 
  of 
  

   stomata 
  it 
  was 
  stated 
  that 
  carbon 
  dioxide 
  may 
  pass 
  into 
  the 
  

   interior 
  of 
  the 
  leaf. 
  It 
  was 
  previously 
  found 
  that 
  water 
  is 
  

   taken 
  into 
  the 
  plant 
  and 
  carried 
  through 
  the 
  stem. 
  In 
  the 
  

   soil 
  are 
  many 
  substances 
  which 
  are 
  dissolved 
  by 
  the 
  water, 
  

   just 
  as 
  common 
  salt 
  or 
  sugar 
  would 
  be. 
  From 
  this 
  source 
  

   there 
  may 
  pass 
  into 
  the 
  plant 
  compounds 
  containing 
  such 
  

   things 
  as 
  nitrogen, 
  potassium, 
  phosphorus, 
  sulphur, 
  and 
  iron. 
  

   Carbon 
  dioxide, 
  which 
  is 
  secured 
  through 
  the 
  surface 
  of 
  the 
  

   leaf, 
  is 
  a 
  gaseous 
  substance 
  which 
  exists 
  in 
  the 
  atmosphere, 
  

  

  