﻿THE 
  STEM 
  AND 
  THE 
  LEAF 
  

  

  59 
  

  

  going 
  to 
  outstrip 
  the 
  corn, 
  but 
  if 
  they 
  are 
  kept 
  down 
  until 
  the 
  

   corn 
  has 
  begun 
  to 
  shade 
  the 
  ground 
  well, 
  there 
  will 
  be 
  little 
  

   further 
  trouble 
  from 
  

   most 
  weeds. 
  If, 
  how- 
  

   ever, 
  the 
  corn 
  is 
  cut 
  

   early 
  for 
  green 
  fodder 
  

   or 
  for 
  ensilage, 
  a 
  rank 
  

   crop 
  of 
  weeds 
  will 
  

   spring 
  up 
  between 
  

   the 
  rows. 
  So 
  foxtail 
  

   and 
  other 
  weeds 
  be- 
  

   gin 
  to 
  flourish 
  among 
  

   the 
  stubble 
  as 
  soon 
  

   as 
  oats, 
  wheat, 
  or 
  rye 
  

   have 
  been 
  reaped. 
  

  

  The 
  stem, 
  then, 
  by 
  

   lifting 
  the 
  leaves 
  up 
  

   into 
  the 
  sunlight 
  and 
  

   supporting 
  them 
  there 
  

   in 
  favorable 
  positions 
  

   (fig. 
  39), 
  gives 
  them 
  

   a 
  chance 
  to 
  do 
  pho- 
  

   tosynthetic 
  work, 
  so 
  

   that 
  the 
  whole 
  plant 
  

   prospers. 
  Even 
  climb- 
  

   ing 
  plants 
  like 
  the 
  

   English 
  ivy 
  (fig. 
  40), 
  

   with 
  stems 
  that 
  bend 
  

   away 
  from 
  the 
  light 
  

   toward 
  a 
  supporting 
  

   rock 
  or 
  tree 
  trunk, 
  

   turn 
  their 
  leaves 
  to 
  

   face 
  the 
  light. 
  There 
  

   are 
  many 
  plants 
  - 
  

   creeping 
  kinds, 
  like 
  white 
  clover, 
  and 
  those 
  with 
  flattish 
  clus- 
  

   ters 
  of 
  leaves, 
  like 
  the 
  dandelion 
  - 
  - 
  which 
  flourish 
  in 
  places 
  

  

  FIG. 
  40. 
  An 
  English 
  ivy 
  (Hedera) 
  grown 
  in 
  

   front 
  of 
  a 
  south 
  window 
  

  

  WW, 
  the 
  line 
  of 
  the 
  window 
  casing 
  ; 
  all 
  to 
  the 
  left 
  

   of 
  this 
  is 
  unlighted 
  wall. 
  The 
  tips 
  of 
  the 
  shoots 
  (0 
  

   avoid 
  the 
  light 
  ; 
  the 
  young 
  leaves 
  (0 
  have 
  assumed 
  

   no 
  definite 
  position 
  ; 
  the 
  mature 
  leaves 
  are 
  nearly 
  

   at 
  right 
  angles 
  to 
  the 
  light 
  coming 
  from 
  the 
  direc- 
  

   tion 
  of 
  the 
  arrow 
  

  

  