﻿FOODS 
  IN 
  PLANTS 
  

  

  39 
  

  

  IT 
  

  

  some 
  of 
  the 
  compounds 
  of 
  nitrogen, 
  potassium, 
  phosphorus, 
  or 
  

   other 
  substances, 
  these 
  things 
  may 
  be 
  made 
  into 
  more 
  complex 
  

   foods 
  known 
  as 
  proteins. 
  

   Many 
  stages 
  of 
  the 
  process 
  

   of 
  making 
  these 
  more 
  coin- 
  

   plex 
  foods 
  are 
  not 
  known, 
  

   and 
  these 
  are 
  too 
  intricate 
  for 
  ex- 
  

   tended 
  discussion 
  at 
  this 
  time. 
  The 
  

   leaf 
  or 
  other 
  parts 
  of 
  the 
  plant 
  may 
  

   be 
  used 
  as 
  the 
  place 
  where 
  proteins 
  

   are 
  made. 
  They 
  may 
  be 
  made 
  im- 
  

   mediately 
  after 
  the 
  carbohydrates, 
  

   or 
  later, 
  but 
  sooner 
  or 
  later 
  some 
  

   protein 
  food 
  is 
  as 
  necessary 
  to 
  the 
  

   continued 
  life 
  of 
  plants 
  as 
  of 
  animals. 
  

   The 
  soil 
  is 
  the 
  usual 
  source 
  of 
  the 
  

   nitrogen, 
  potassium, 
  phosphorus, 
  

   and 
  other 
  substances 
  that 
  are 
  used 
  

   in 
  addition 
  to 
  the 
  carbohydrates 
  in 
  

   making 
  proteins. 
  Although 
  the 
  air 
  

   is 
  78 
  per 
  cent 
  nitrogen, 
  this 
  atmos- 
  

   pheric 
  nitrogen 
  is 
  not 
  available 
  to 
  

   plants, 
  except 
  to 
  certain 
  bacteria 
  

   which 
  are 
  to 
  be 
  discussed 
  later. 
  

   From 
  the 
  soil, 
  compounds 
  contain- 
  

   ing 
  nitrogen 
  and 
  other 
  substances 
  

   may 
  be 
  dissolved 
  in 
  water 
  and 
  then 
  

   carried 
  into 
  the 
  plants. 
  Fertile 
  soils 
  

   are 
  those 
  which 
  contain 
  in 
  available 
  

  

  .p^, 
  , 
  i 
  ,-, 
  ,. 
  ,1 
  .-, 
  . 
  stems 
  and 
  crowd 
  out 
  some 
  water 
  

  

  form 
  large 
  quantities 
  of 
  the 
  things 
  from 
  the 
  previously 
  filled 
  grad- 
  

  

  wllich 
  plants 
  USe 
  for 
  food-making. 
  uate 
  - 
  The 
  ordinary 
  test 
  for 
  oxy- 
  

   T> 
  __]-. 
  '1 
  i 
  f 
  S 
  en 
  with 
  a 
  burning 
  stick 
  will 
  

  

  Replenishment 
  and 
  growth 
  of 
  new 
  determine 
  whether 
  It 
  is 
  present. 
  

  

  FIG. 
  27. 
  Apparatus 
  for 
  collect- 
  

   ing 
  oxygen 
  from 
  working 
  plants 
  

  

  Water 
  plants 
  are 
  submerged 
  with 
  

   one 
  end 
  in 
  the 
  mouth 
  of 
  the 
  grad- 
  

   uate. 
  Bubbles 
  of 
  oxygen 
  pass 
  

   upward 
  from 
  the 
  cut 
  ends 
  of 
  the 
  

  

  parts 
  can 
  take 
  place 
  only 
  by 
  means 
  In 
  such 
  an 
  experiment 
  care 
  must 
  

  

  ~f 
  ,-] 
  ,,i 
  A.-I 
  i 
  

  

  of 
  foods, 
  and 
  since 
  the 
  plant 
  makes 
  

  

  its 
  Own 
  Supply, 
  the 
  importance 
  of 
  in 
  tube, 
  to 
  permit 
  free 
  passage 
  

  

  the 
  process 
  i. 
  very 
  great. 
  

  

  <" 
  

  

  