﻿APPENDIX 
  

   PHOTOSYNTHESIS 
  

  

  The 
  chemistry 
  of 
  photosynthesis 
  is 
  not 
  completely 
  known, 
  

   but 
  some 
  of 
  the 
  simpler 
  aspects 
  of 
  it 
  may 
  prove 
  valuable 
  to 
  

   the 
  student. 
  The 
  chemist's 
  formula 
  for 
  water 
  is 
  H 
  2 
  O, 
  in 
  

   which 
  H 
  stands 
  for 
  hydrogen 
  and 
  O 
  for 
  oxygen, 
  and 
  the 
  

   figure 
  2 
  indicates 
  that 
  two 
  parts 
  of 
  hydrogen 
  are 
  united 
  with 
  

   one 
  part 
  of 
  oxygen. 
  Similarly, 
  CO 
  2 
  indicates 
  that 
  one 
  part 
  

   of 
  carbon 
  is 
  united 
  with 
  two 
  parts 
  of 
  oxygen 
  to 
  form 
  carbon 
  

   dioxide. 
  When 
  these 
  compounds 
  are 
  broken 
  up, 
  there 
  is, 
  for 
  

   a 
  very 
  brief 
  time 
  at 
  least, 
  free 
  C, 
  H, 
  and 
  O. 
  If 
  one 
  unit 
  of 
  

   each 
  compound 
  (H 
  O 
  and 
  CO.,) 
  is 
  thus 
  broken 
  up, 
  there 
  

   will 
  be 
  two 
  H, 
  one 
  O, 
  one 
  C, 
  and 
  two 
  O 
  - 
  - 
  or 
  in 
  all 
  three 
  O. 
  

   After 
  photosynthesis 
  has 
  been 
  going 
  on 
  for 
  some 
  time, 
  starch 
  

   is 
  usually 
  formed. 
  Starch 
  consists 
  of 
  (C 
  6 
  H 
  1Q 
  O 
  5 
  ) 
  W 
  . 
  This 
  

   means 
  that 
  six 
  parts 
  of 
  carbon, 
  ten 
  parts 
  of 
  hydrogen, 
  and 
  five 
  

   parts 
  of 
  oxygen 
  unite 
  to 
  form 
  starch, 
  and 
  the 
  n 
  means 
  that 
  

   the 
  unit 
  C 
  6 
  H 
  1Q 
  O 
  5 
  does 
  not 
  appear 
  singly, 
  but 
  that 
  an 
  unknown 
  

   number 
  of 
  them 
  are 
  united. 
  Disregarding 
  the 
  fact 
  that 
  several 
  

   of 
  the 
  starch 
  units 
  are 
  held 
  together, 
  and 
  considering 
  the 
  single 
  

   unit 
  C 
  6 
  H 
  1Q 
  O 
  6 
  , 
  we 
  may 
  be 
  able 
  to 
  see 
  what 
  happens 
  in 
  the 
  work 
  

   of 
  photosynthesis. 
  To 
  secure 
  the 
  amount 
  of 
  carbon 
  necessary 
  

   to 
  form 
  starch, 
  six 
  times 
  the 
  unit 
  CO 
  must 
  be 
  taken, 
  since 
  

   six 
  units 
  of 
  carbon 
  are 
  to 
  be 
  used. 
  To 
  secure 
  the 
  needed 
  

   amount 
  of 
  hydrogen, 
  five 
  times 
  the 
  unit 
  H 
  O 
  must 
  be 
  used, 
  

   since 
  there 
  must 
  be 
  ten 
  units 
  of 
  hydrogen, 
  and 
  two 
  are 
  secured 
  

   with 
  each 
  unit 
  of 
  water. 
  We 
  have 
  therefore 
  6 
  (CO 
  2 
  ) 
  and 
  

   5 
  (H 
  2 
  O). 
  When 
  the 
  energy 
  of 
  the 
  sun 
  has 
  broken 
  these 
  

   things 
  into 
  their 
  constituent 
  parts, 
  there 
  are 
  6 
  (C), 
  12 
  (O), 
  

   10 
  (H), 
  and 
  5 
  (O) 
  or 
  17 
  (O) 
  in 
  all. 
  But 
  starch 
  consists 
  of 
  

  

  343 
  

  

  