﻿CHAPTER 
  IV 
  

  

  MANUFACTURE, 
  TRANSPORTATION, 
  AND 
  USE 
  OF 
  

   FOODS 
  IN 
  PLANTS 
  

  

  32. 
  The 
  problem 
  of 
  securing 
  food. 
  Plants, 
  like 
  animals, 
  can- 
  

   not 
  continue 
  to 
  live 
  and 
  grow 
  without 
  nourishment, 
  but 
  like 
  

   animals, 
  they 
  may 
  secure 
  the 
  needed 
  nourishment 
  in 
  a 
  variety 
  

   of 
  ways. 
  Reference 
  has 
  already 
  been 
  made 
  to 
  some 
  of 
  the 
  ways 
  

   in 
  which 
  roots, 
  stems, 
  and 
  leaves 
  are 
  related 
  to 
  the 
  plant's 
  food 
  

   supply, 
  but 
  wo 
  shall 
  need 
  to 
  consider 
  further 
  the 
  machinery 
  

   and 
  processes 
  by 
  means 
  of 
  which 
  green 
  plants 
  manufacture 
  

   the 
  things 
  that 
  nourish 
  them. 
  

  

  33. 
  Structure 
  of 
  a 
  leaf 
  ; 
  epidermis. 
  In 
  Chapter 
  II 
  the 
  gen- 
  

   eral 
  form 
  of 
  the 
  leaf 
  and 
  some 
  of 
  its 
  functions 
  were 
  discussed. 
  

   A 
  more 
  detailed 
  study 
  of 
  leaf 
  structure 
  and 
  function 
  is 
  neces- 
  

   sary 
  for 
  the 
  discussions 
  of 
  the 
  present 
  chapter. 
  

  

  Most 
  leaves 
  consist 
  of 
  the 
  petiole, 
  or 
  leafstalk, 
  and 
  the 
  blade, 
  

   or 
  expanded 
  portion. 
  In 
  some 
  leaves 
  there 
  is 
  no 
  petiole; 
  

   that 
  is, 
  the 
  leaf 
  is 
  .sT.s-.s-/A-, 
  or 
  rests 
  directly 
  upon 
  the 
  stem 
  or 
  

   branch 
  that 
  bears 
  it. 
  In 
  some 
  leaves 
  the 
  blade 
  is 
  divided 
  into 
  

   several 
  parts, 
  or 
  leaflets. 
  An 
  undivided 
  leaf 
  is 
  */////</,, 
  and 
  a 
  

   divided 
  leaf 
  is 
  coin/xmii,/. 
  Leaves 
  vary 
  in 
  size, 
  from 
  those 
  

   that 
  are 
  so 
  small 
  that 
  they 
  are 
  not 
  readily 
  visible, 
  to 
  those 
  so 
  

   huge 
  that 
  they 
  are 
  several 
  feet 
  in 
  width 
  or 
  several 
  yards 
  in 
  

   length. 
  In 
  color 
  most 
  leaves 
  are 
  green, 
  but 
  they 
  differ 
  in 
  

   strength 
  of 
  color, 
  and 
  a 
  careful 
  observation 
  usually 
  discloses 
  

   a 
  difference 
  in 
  greenness 
  between 
  the 
  two 
  leaf 
  surfaces, 
  or 
  

   between 
  different 
  parts 
  of 
  the 
  same 
  surface. 
  It 
  is 
  possible 
  to 
  

   observe 
  within 
  most 
  leaves 
  the 
  more 
  or 
  less 
  regularly 
  arranged 
  

   veins, 
  or 
  fibrovascular 
  bundles, 
  which 
  are 
  not 
  green. 
  Also 
  on 
  

   one 
  or 
  both 
  leaf 
  surfaces, 
  as 
  in 
  the 
  mullein, 
  begonia, 
  and 
  thistle, 
  

   there 
  often 
  develop 
  outgrowths 
  known 
  as 
  hairs. 
  

  

  34 
  

  

  