﻿Vegetable 
  Assimilation 
  and 
  Respiration. 
  261 
  

  

  distinct 
  chlorophyll 
  and 
  no 
  assimilation 
  to 
  the 
  later 
  phase 
  where, 
  with 
  still 
  

   little 
  chlorophyll, 
  the 
  photosynthesis 
  is 
  quite 
  large. 
  

  

  Irving's 
  experiments 
  also 
  show 
  that 
  the 
  assimilatory 
  power 
  goes 
  on 
  

   developing, 
  though 
  further 
  greening 
  is 
  arrested 
  by 
  darkness, 
  a 
  point 
  demon- 
  

   strated 
  by 
  the 
  writer's 
  experiments. 
  For 
  example, 
  in 
  her 
  second 
  experiment, 
  

   although, 
  after 
  having 
  developed 
  a 
  considerable 
  tint 
  of 
  green, 
  the 
  leaves 
  

   showed 
  no 
  reduction 
  of 
  respiratory 
  carbon 
  dioxide, 
  yet 
  after 
  the 
  lapse 
  of 
  

   18 
  hours, 
  though 
  further 
  greening 
  was 
  inhibited 
  by 
  darkening 
  overnight, 
  they 
  

   showed 
  definite 
  signs 
  of 
  photosynthesis 
  on 
  lighting 
  again. 
  

  

  The 
  Photosynthesis 
  of 
  Young 
  Leaves 
  Developing 
  on 
  Mature 
  Plants. 
  

   A 
  consideration 
  of 
  Willstatter 
  's 
  work 
  on 
  developing 
  leaves 
  of 
  trees 
  in 
  

   spring 
  and 
  on 
  the 
  leaves 
  of 
  golden 
  varieties 
  very 
  poor 
  in 
  chlorophyll 
  adds 
  

   further 
  support 
  to 
  the 
  conclusions 
  drawn 
  above. 
  

  

  Table 
  D. 
  — 
  Relation 
  of 
  Photosynthesis 
  to 
  Amount 
  of 
  Chlorophyll 
  in 
  Different 
  

   Types 
  of 
  Leaves 
  of 
  Qucrcus 
  Robur 
  (Willstatter 
  and 
  Stoll). 
  Conditions 
  of 
  

   experimentation 
  the 
  same 
  as 
  in 
  Table 
  C. 
  

  

  Date. 
  

  

  Description. 
  

  

  Chlorophyll- 
  

   content. 
  

  

  ] 
  

  

  . 
  . 
  -i 
  ,. 
  Assimilation 
  

   Assimilation. 
  • 
  , 
  

  

  number. 
  

  

  1 
  

  

  May 
  2 
  . 
  

  

  „ 
  20 
  

  

  July 
  20 
  

  

  „ 
  18 
  

  

  Normal 
  young 
  

  

  „ 
  older 
  

   Golden 
  variety 
  

  

  6 
  6 
  

   8 
  6 
  

   21 
  6 
  

   25 
  

   1 
  9 
  

  

  0-072 
  

   0-136 
  

   0-194 
  

   0-196 
  

   0-103 
  

  

  10 
  9 
  

   15-8 
  

   ' 
  9 
  

   7-8 
  

   55 
  -0 
  

  

  Note. 
  — 
  Chlorophyll- 
  content 
  and 
  assimilation 
  are 
  given 
  in 
  same 
  units 
  as 
  in 
  Table 
  C. 
  

  

  In 
  considering 
  these 
  results 
  it 
  will 
  be 
  as 
  well 
  to 
  bear 
  in 
  mind 
  the 
  con- 
  

   clusions 
  arrived 
  at 
  previously 
  as 
  'to 
  the 
  interconnection 
  of 
  external 
  conditions 
  

   and 
  internal 
  limiting 
  factors. 
  

  

  Since 
  the 
  two 
  older 
  samples 
  of 
  green 
  leaves 
  give 
  the 
  same 
  assimilation 
  

   with 
  different 
  chlorophyll-content, 
  it 
  may 
  be 
  assumed 
  that, 
  under 
  these 
  

   experimental 
  conditions, 
  the 
  photochemical 
  stage 
  is 
  not 
  limiting. 
  Further 
  

   evidence 
  is 
  supplied 
  by 
  the 
  fact 
  that 
  other 
  experiments 
  of 
  Willstatter 
  show 
  

   that 
  normal 
  green 
  leaves 
  at 
  25° 
  C. 
  reach 
  their 
  maximum 
  assimilation 
  with 
  

   half 
  the 
  above 
  light 
  (about 
  24,000 
  lux). 
  That 
  the 
  assimilation 
  of 
  the 
  golden 
  

   variety 
  is 
  limited 
  by 
  the 
  photochemical 
  stage 
  is 
  indicated 
  by 
  the 
  fact 
  that 
  

   the 
  assimilation, 
  with 
  the 
  smaller 
  chlorophyll-content, 
  is 
  less 
  than 
  that 
  of 
  

   the 
  normal 
  leaves, 
  and 
  that 
  even 
  at 
  48,000 
  lux 
  the 
  leaves 
  show 
  no 
  signs 
  of 
  

   having 
  reached 
  their 
  maximum 
  of 
  assimilation. 
  Most 
  probably, 
  with 
  still 
  

   further 
  increase 
  of 
  illumination 
  and 
  the 
  temperature 
  still 
  25° 
  C, 
  they 
  would 
  

  

  