﻿Vegetable 
  Assimilation 
  and 
  Respiration. 
  259 
  

  

  temperature 
  of 
  the 
  bath 
  in 
  which 
  the 
  leaf-chamber 
  was 
  placed, 
  and 
  con- 
  

   sequently 
  the 
  leaf-temperature 
  was 
  increased 
  on 
  illumination. 
  Willstatter 
  

   has 
  shown 
  in 
  other 
  experiments 
  that 
  leaves 
  give 
  up 
  carbon 
  dioxide 
  when 
  the 
  

   temperature 
  is 
  raised. 
  This, 
  however, 
  continues 
  for 
  about 
  an 
  hour 
  only. 
  

   A 
  consideration 
  of 
  the 
  small 
  amount 
  of 
  carbon 
  dioxide 
  in 
  the 
  air 
  current, 
  the 
  

   small 
  change 
  of 
  temperature, 
  and 
  the 
  duration 
  of 
  Irving's 
  experiments, 
  shows 
  

   that 
  this 
  source 
  of 
  error 
  is 
  negligible. 
  Willstatter 
  also 
  agrees 
  that 
  this 
  

   detail 
  in 
  Irving's 
  method 
  of 
  experimentation 
  cannot 
  be 
  the 
  cause 
  of 
  her 
  

   results 
  being 
  different 
  from 
  his 
  own.* 
  

  

  Under 
  conditions 
  of 
  more 
  concentrated 
  carbon 
  dioxide 
  supply, 
  he 
  found 
  

   that, 
  with 
  increasing 
  chlorophyll-content, 
  the 
  leaves 
  showed 
  increasing 
  

   assimilation. 
  The 
  following 
  Table 
  is 
  an 
  extract 
  from 
  his 
  results 
  obtained 
  . 
  

   with 
  Phaseolus 
  : 
  — 
  

  

  Table 
  C. 
  — 
  Experiments 
  of 
  Willstatter 
  and 
  Stoll 
  on 
  Photosynthesis 
  with 
  

  

  Etiolated 
  Phaseolus. 
  

  

  Carbon 
  dioxide 
  5 
  per 
  cent 
  ; 
  illumination 
  48,000 
  lux 
  ; 
  temperature 
  25° 
  C. 
  

  

  Exposure 
  to 
  light 
  

   for 
  greening. 
  

  

  Colour 
  of 
  

   leaves. 
  

  

  Chlorophyll 
  per 
  

   10 
  grm. 
  

   fresh 
  weight. 
  

  

  Assimilation 
  C0 
  2 
  

   per 
  10 
  grm. 
  

   fresh 
  weight 
  

   per 
  hour. 
  

  

  Assimilation 
  

   number. 
  

  

  

  

  mgrm. 
  

  

  grms. 
  

  

  

  

  

  Yellow 
  

  

  <o-i 
  

  

  -014 
  

  

  

  >70 
  

  

  Six 
  hours 
  

  

  Green-yellow 
  

  

  0-6 
  

  

  -080 
  

  

  

  133 
  

  

  Two 
  days 
  

  

  Yellow-green 
  

  

  8-0 
  

  

  0-172 
  

  

  

  24 
  

  

  

  Grass 
  green 
  

  

  15 
  6 
  

  

  -204 
  

  

  

  13 
  3 
  

  

  Grown 
  in 
  light 
  ; 
  

  

  normal 
  green 
  

  

  18-6 
  

  

  0-174 
  

  

  

  9-4 
  

  

  j0rgensen 
  and 
  Stiles,t 
  in 
  their 
  review 
  of 
  the 
  literature 
  on 
  carbon 
  

   assimilation, 
  agree 
  with 
  Willstatter 
  that 
  the 
  latter's 
  results 
  show, 
  contrary 
  

   to 
  Irving's 
  conclusion, 
  that, 
  during 
  the 
  development 
  of 
  chlorophyll, 
  it 
  is 
  this 
  

   factor 
  which 
  is 
  limiting 
  the 
  assimilation. 
  They 
  suggest 
  that 
  possibly 
  Irving's 
  

   results 
  were 
  due 
  to 
  light 
  being 
  limiting. 
  

  

  The 
  only 
  grounds 
  they 
  give 
  for 
  the 
  conclusion 
  that 
  Willstatter 
  has 
  shown 
  

   chlorophyll 
  to 
  be 
  the 
  limiting 
  factor 
  is 
  the 
  fact 
  that 
  the 
  partially 
  greened 
  

   leaves 
  have 
  high 
  assimilation 
  numbers, 
  that 
  is, 
  high 
  compared 
  with 
  normal 
  

   leaves. 
  Consideration, 
  however, 
  indicates 
  that 
  the 
  only 
  conclusion 
  to 
  be 
  

   drawn 
  is 
  that, 
  with 
  increasing 
  chlorophyll-content, 
  the 
  assimilation 
  does 
  not 
  

   increase 
  proportionately 
  ; 
  constancy 
  of 
  assimilation 
  number, 
  with 
  rising 
  

  

  * 
  Willstatter, 
  E., 
  and 
  Stoll, 
  A., 
  ' 
  TJntersuchungen 
  iiber 
  die 
  Assimilation 
  der 
  

   Kohlensiiure,' 
  Berlin, 
  1918, 
  p. 
  131. 
  

  

  t 
  J0rgensen, 
  I., 
  and 
  Stiles, 
  W., 
  " 
  Carbon 
  Assimilation," 
  ' 
  New 
  Phytologist,' 
  vol. 
  15, 
  

   p. 
  184 
  (1916). 
  

  

  