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  INTRODUCTION 
  TO 
  BOTANY 
  

  

  to 
  corn. 
  Their 
  nourishment 
  consists 
  of 
  the 
  juices 
  which 
  they 
  

   suck 
  from 
  the 
  tender 
  roots. 
  They 
  excrete 
  a 
  sweetish 
  sub- 
  

   stance 
  called 
  honeyde\v, 
  which 
  is 
  used 
  as 
  food 
  by 
  ants 
  and 
  

   sometimes 
  by 
  other 
  kinds 
  of 
  insects. 
  The 
  apliids 
  may 
  begin 
  to 
  

   live 
  upon 
  corn 
  when 
  the 
  seedling 
  is 
  germinating, 
  and 
  continue 
  

   upon 
  the 
  growing 
  plant 
  until 
  it 
  is 
  mature. 
  The 
  apliids 
  are 
  

   sluggish 
  insects 
  and, 
  although 
  they 
  reproduce 
  rapidly 
  when 
  

   food 
  is 
  abundant, 
  they 
  are 
  not 
  readily 
  able 
  to 
  pass 
  through 
  

   the 
  soil 
  or 
  over 
  its 
  surface 
  to 
  the 
  roots 
  of 
  new 
  plants. 
  

  

  There 
  is 
  a 
  common 
  black 
  Held 
  ant 
  which 
  devours 
  the 
  honey- 
  

   dew, 
  apparently 
  with 
  great 
  relish. 
  The 
  burrows 
  of 
  these 
  ants 
  

   may 
  often 
  be 
  seen 
  about 
  the 
  bases 
  of 
  corn 
  plants. 
  They 
  dig 
  

   tunnels 
  to 
  the 
  roots 
  of 
  the 
  corn, 
  then 
  carry 
  down 
  some 
  of 
  the 
  

   aphids 
  and 
  place 
  them 
  upon 
  the 
  roots. 
  There 
  the 
  apliids 
  are 
  

   cared 
  for 
  by 
  the 
  ants, 
  and 
  the 
  latter 
  secure 
  the 
  honeydew 
  as 
  

   food. 
  Throughout 
  the 
  summer 
  and 
  autumn 
  the 
  ants 
  con- 
  

   stantly 
  care 
  for 
  the 
  aphids 
  and 
  their 
  young. 
  Aphid 
  eggs 
  

   are 
  carried 
  to 
  the 
  places 
  that 
  are 
  most 
  favorable 
  for 
  their 
  

   hatching, 
  and 
  when 
  the 
  young 
  are 
  hatched 
  they 
  are 
  trans- 
  

   planted 
  upon 
  tender 
  young 
  roots. 
  When 
  disturbances 
  of 
  the 
  

   soil 
  threaten 
  destruction 
  to 
  the 
  eggs, 
  the 
  ants 
  seize 
  them 
  as 
  

   they 
  would 
  their 
  own 
  eggs 
  and 
  carry 
  them 
  away. 
  At 
  the 
  be- 
  

   ginning 
  of 
  the 
  winter 
  aphid 
  eggs 
  are 
  carried 
  by 
  the 
  ants 
  into 
  

   the 
  deepest 
  parts 
  of 
  the 
  ant 
  nests. 
  At 
  the 
  return 
  of 
  the 
  favor- 
  

   able 
  season 
  the 
  eggs 
  are 
  brought 
  forth 
  again 
  to 
  places 
  suitable 
  

   for 
  hatching. 
  In 
  this 
  case 
  the 
  aphids, 
  which 
  are 
  parasitic 
  upon 
  

   the 
  corn 
  roots, 
  are 
  themselves 
  in 
  slavery 
  (Ji<'ltixin') 
  to 
  the 
  ants, 
  

   and 
  this 
  interrelation 
  obviously 
  reaches 
  a 
  high 
  degree 
  of 
  de- 
  

   velopment. 
  When 
  seed 
  corn 
  is 
  treated 
  with 
  oil 
  of 
  lemon, 
  the 
  

   aphids 
  are 
  said 
  to 
  be 
  repelled, 
  for 
  a 
  time 
  at 
  least, 
  from 
  the 
  

   young 
  plants. 
  Frequent 
  cultivation 
  disturbs 
  the 
  ant 
  burrows, 
  

   and 
  birds 
  that 
  prey 
  upon 
  ants, 
  as 
  flickers 
  and 
  woodpeckers, 
  

   also 
  tend 
  to 
  reduce 
  the 
  damage 
  done 
  by 
  the 
  aphids. 
  

  

  309. 
  Resistance 
  to 
  disease. 
  Every 
  kind 
  of 
  economic 
  plant 
  

   seems 
  to 
  have 
  one 
  or 
  more 
  plant 
  or 
  animal 
  diseases. 
  Each 
  

   presents 
  special 
  problems, 
  many 
  of 
  which 
  are 
  yet 
  unsolved. 
  

  

  