﻿268 
  ■ 
  MacDougal: 
  Growth 
  of 
  the 
  tomato 
  

  

  f 
  

  

  ' 
  2, 
  The 
  rate 
  of 
  increase 
  in 
  diameter 
  of 
  such 
  globose, 
  berry-like 
  

   fruits 
  is 
  not 
  a 
  correct 
  or 
  even 
  approximate 
  measure 
  of 
  actual 
  

   growth 
  considered 
  as 
  an 
  accretion 
  of 
  water 
  and 
  solid 
  material. 
  

  

  3. 
  The 
  time 
  at 
  which 
  the 
  greatest 
  increase 
  in 
  diameter 
  takes 
  

   place 
  may 
  coincide 
  with 
  the 
  greatest 
  growth 
  as 
  exemplified 
  in 
  

   previously 
  described 
  observations, 
  but 
  the 
  increase 
  in 
  thickness 
  is 
  

   not 
  a 
  direct 
  index 
  of 
  growth 
  in 
  such 
  bodies. 
  Actual 
  growth 
  

   varies 
  as 
  the 
  cube 
  of 
  the 
  radius. 
  

  

  4. 
  The 
  culmination 
  of 
  the 
  rate 
  may 
  not 
  be 
  reached 
  until 
  

   the 
  fruit 
  is 
  in 
  a 
  stage 
  approaching 
  maturity. 
  The 
  maximum 
  accre- 
  

   tion 
  generally 
  takes 
  place 
  in 
  a 
  stage 
  subsequent 
  to 
  the 
  highest 
  

   rate 
  of 
  increase 
  of 
  the 
  diameter. 
  

  

  5. 
  The 
  internal 
  factors 
  which 
  determine 
  the 
  rate 
  and 
  amount 
  

   of 
  growth 
  of 
  the 
  tomato 
  include 
  the 
  soluble 
  sugars 
  and 
  the 
  salts 
  or 
  

   bases 
  which 
  increase 
  toward 
  maturity, 
  and 
  the 
  albumins 
  and 
  

   celluloses 
  which 
  decrease 
  with 
  development, 
  while 
  the 
  amino- 
  

   acids, 
  not 
  determined, 
  probably 
  do 
  not 
  vary 
  so 
  widely 
  as 
  to 
  affect 
  

   their 
  value 
  as 
  growth 
  accelerators. 
  . 
  

  

  6. 
  The 
  conjunction 
  of 
  low 
  acidity 
  and 
  low 
  salt 
  content 
  and 
  

   sugar 
  content 
  would 
  give 
  a 
  set 
  of 
  conditions 
  for 
  high 
  imbibitional 
  

   swelling 
  of 
  a 
  pentosan-protein 
  plasma 
  in 
  the 
  earlier 
  stages 
  of 
  

   growth 
  which 
  would 
  be 
  capable 
  of 
  carrying 
  the 
  fruit 
  to 
  an 
  enlarge- 
  

   ment 
  of 
  3,000 
  to 
  4,000 
  per 
  cent 
  of 
  the 
  dry 
  matter, 
  as 
  determined 
  

   by 
  previous 
  experiments 
  in 
  the 
  hydration 
  of 
  such 
  colloids. 
  Other- 
  

   wise 
  expressed, 
  Imbibition 
  would 
  be 
  capable 
  of 
  making 
  a 
  colloidal 
  

   body 
  like 
  a 
  fruit 
  which 
  would 
  consist 
  of 
  97.5 
  per 
  cent 
  water 
  and 
  

   2,5 
  per 
  cent 
  solid 
  matter. 
  

  

  7. 
  The 
  higher 
  salt 
  content 
  and 
  acidity 
  of 
  older 
  fruits 
  would 
  

   operate 
  to 
  lessen 
  imbibition 
  in 
  the 
  fruits, 
  which 
  in 
  this 
  stage 
  would 
  

  

  ^ 
  be 
  high 
  in 
  carbohydrates. 
  

  

  8. 
  The 
  above 
  facts 
  support 
  the 
  conclusion 
  that 
  the 
  distentive 
  

   force 
  in 
  growth 
  of 
  young 
  fruits 
  is 
  chiefly 
  imbibition. 
  Osmotic 
  

   action 
  may 
  play 
  the 
  more 
  important 
  part 
  in 
  later 
  stages. 
  

  

  9. 
  The 
  growth 
  of 
  a 
  fruit 
  therefore 
  is 
  a 
  resultant 
  of 
  two 
  groups 
  

   of 
  activities, 
  one 
  ordinarily 
  classed 
  as 
  imbibitional 
  and 
  the 
  other 
  

   associated 
  with 
  osmosis 
  and 
  turgidity. 
  

  

  10. 
  Young 
  fruits 
  include 
  i 
  to 
  4 
  per 
  cent 
  more 
  solid 
  material 
  

   than 
  mature 
  ones, 
  these 
  bodies 
  being 
  representative 
  of 
  a 
  type 
  of 
  

  

  I 
  

  

  