﻿262 
  Mr. 
  G. 
  E. 
  Briggs. 
  Experimental 
  Researches 
  on 
  

  

  reach 
  the 
  same 
  maximum 
  as 
  the 
  green 
  leaves, 
  provided 
  the 
  chemical 
  stage 
  

   allowed 
  of 
  such 
  activity. 
  

  

  It 
  is 
  interesting 
  that, 
  when 
  through 
  weak 
  illumination, 
  the 
  photochemical 
  

   stage 
  is 
  limiting 
  in 
  both 
  the 
  mature 
  green 
  and 
  the 
  golden 
  leaves, 
  the 
  assimi- 
  

   lation 
  is 
  not 
  proportional 
  to 
  the 
  chlorophyll-content, 
  the 
  ratio 
  of 
  the 
  former 
  

   to 
  the 
  latter 
  being 
  greater 
  in 
  the 
  golden 
  variety. 
  

  

  These 
  facts 
  may 
  be 
  expressed 
  as 
  follows 
  in 
  terms 
  of 
  Willstatter's 
  assimi- 
  

   lation 
  number. 
  With 
  the 
  temperature 
  at 
  25° 
  C. 
  the 
  assimilation 
  number 
  of 
  

   both 
  types 
  of 
  leaves 
  increases 
  with 
  increase 
  of 
  illumination 
  from 
  zero 
  to 
  

   24,000 
  lux, 
  since 
  the 
  assimilation 
  increases 
  without 
  change 
  in 
  the 
  chlorophyll- 
  

   content. 
  Throughout 
  this 
  range 
  the 
  assimilation 
  numbers 
  of 
  the 
  golden 
  

   leaves 
  are 
  much 
  greater 
  than 
  those 
  of 
  the 
  normal 
  green 
  leaves. 
  On 
  further 
  

   increasing 
  the 
  illumination 
  beyond 
  24,000 
  lux, 
  the 
  assimilation 
  number 
  of 
  

   the 
  green 
  leaves 
  remains 
  constant, 
  but 
  that 
  of 
  the 
  golden 
  variety 
  continues 
  

   to 
  increase 
  until 
  the 
  maximum 
  of 
  assimilation 
  is 
  reached 
  at 
  a 
  point 
  where 
  

   the 
  chemical 
  stage 
  becomes 
  limiting. 
  Since, 
  under 
  all 
  conditions 
  of 
  illumi- 
  

   nation, 
  the 
  assimilation 
  numbers 
  of 
  the 
  golden 
  leaves 
  are 
  higher 
  than 
  those 
  

   of 
  the 
  green, 
  mere 
  comparison 
  of 
  assimilation 
  numbers 
  gives 
  no 
  indication 
  as 
  

   to 
  what 
  stage 
  or 
  factor 
  is 
  limiting. 
  Fuller 
  consideration 
  of 
  illumination 
  and 
  

   chlorophyll-content 
  such 
  as 
  that 
  given 
  above 
  is 
  necessary. 
  

  

  Willstatter 
  comments 
  upon 
  the 
  similarity 
  of 
  his 
  etiolated 
  leaves 
  of 
  small 
  

   chlorophyll-content 
  to 
  the 
  golden 
  varieties, 
  in 
  that 
  both 
  have 
  high 
  assimila- 
  

   tion 
  numbers. 
  This 
  similarity 
  is 
  not 
  surprising, 
  since 
  both 
  types 
  of 
  leaves 
  

   are 
  more 
  or 
  less 
  fully 
  developed 
  except 
  for 
  small 
  chlorophyll-content, 
  and 
  

   since 
  at 
  25° 
  C. 
  and 
  48,000 
  lux 
  the 
  chlorophyll 
  in 
  fully-greened 
  leaves 
  is 
  

   greatly 
  in 
  excess 
  of 
  the 
  amount 
  required 
  for 
  full 
  assimilatory 
  activity. 
  This 
  

   similarity, 
  however, 
  does 
  not 
  warrant 
  any 
  conclusions 
  such 
  as 
  those 
  drawn 
  

   by 
  Willstatter 
  as 
  to 
  the 
  nature 
  of 
  the 
  limiting 
  factor 
  or 
  stage 
  in 
  his 
  etiolated 
  

   leaves. 
  

  

  In 
  the 
  case 
  of 
  Willstatter's 
  etiolated 
  leaves 
  there 
  are 
  no 
  results 
  for 
  material 
  

   which 
  is 
  definitely 
  comparable 
  in 
  protoplasmic 
  development, 
  as 
  there 
  are 
  in 
  

   the 
  case 
  of 
  the 
  mature 
  green 
  and 
  the 
  mature 
  golden 
  leaves 
  considered 
  above. 
  

   In 
  the 
  earlier 
  stages 
  of 
  development 
  of 
  leaves 
  a 
  difference 
  in 
  the 
  age 
  of 
  a 
  

   day 
  may 
  represent 
  a 
  considerable 
  difference 
  in 
  the 
  degree 
  of 
  protoplasmic 
  

   development. 
  Nor 
  are 
  there 
  results 
  for 
  identical 
  material 
  under 
  different 
  

   conditions 
  of 
  illumination, 
  as 
  is 
  the 
  case 
  in 
  our 
  experiments. 
  

  

  An 
  analysis 
  of 
  Willstatter's 
  results 
  for 
  young 
  spring 
  leaves 
  gives 
  definite 
  

   evidence 
  that 
  chlorophyll 
  is 
  not 
  here 
  the 
  factor 
  limiting 
  the 
  assimilation. 
  

   First, 
  since 
  in 
  the 
  youngest 
  sample 
  with 
  a 
  chlorophyll-content 
  of 
  6*6 
  the 
  

   assimilation 
  is 
  only 
  - 
  072, 
  whereas 
  in 
  the 
  golden 
  variety 
  the 
  assimilation 
  is 
  

  

  