﻿266 
  MacDougal: 
  Growth 
  of 
  the 
  tomato 
  

  

  invariably 
  present 
  in 
  cell-masses 
  of 
  this 
  kind. 
  The 
  hydrogen 
  ion 
  

   concentration 
  and 
  the 
  proportion 
  of 
  salts 
  or 
  bases 
  is 
  still 
  low 
  and 
  

   their 
  effect 
  on 
  the 
  swelling 
  would 
  be 
  limited. 
  ,It 
  would 
  therefore 
  

   be 
  possible 
  for 
  these 
  young 
  fruits 
  to 
  make 
  a 
  notable 
  amount 
  of 
  

   growth 
  or 
  expansion 
  upon 
  imbibition 
  by 
  the 
  protein-pentosan 
  

   plasma 
  in 
  a 
  juice 
  relatively 
  low 
  in 
  salts 
  and 
  In 
  acids. 
  

  

  Development 
  and 
  increase 
  in 
  size 
  would 
  however 
  be 
  attended 
  

   by 
  a 
  lessened 
  albumin 
  content, 
  making 
  the 
  plasma 
  react 
  more 
  like 
  

   agar 
  in 
  which 
  hydration 
  is 
  lessened 
  by 
  salts 
  and 
  by 
  acids, 
  and 
  

  

  L 
  

  

  T 
  

  

  imbibitional 
  swelling 
  would 
  be 
  notably 
  decreased. 
  

  

  The 
  accumulation 
  of 
  sugars 
  in 
  the 
  cells 
  occurring 
  concurrently 
  

   with 
  lessened 
  imbibition 
  serves 
  to 
  set 
  up 
  an 
  osmotic 
  mechanism 
  

   by 
  which 
  an 
  increasing 
  turgidity 
  would 
  result, 
  serving 
  as 
  a 
  disten- 
  

   tive 
  agency 
  in 
  the 
  later 
  stages 
  of 
  growth 
  more 
  than 
  replacing 
  the 
  

   waning 
  capacity 
  for 
  imbibition, 
  and 
  the 
  action 
  of 
  osmosis 
  in 
  these 
  

   fruits 
  might 
  have 
  a 
  heightened 
  effect 
  by 
  reason 
  of 
  the 
  fact 
  that 
  

   the 
  cell 
  walls 
  of 
  much 
  of 
  the 
  fruit 
  become 
  ^'pectinated" 
  and 
  

   the 
  proportion 
  of 
  cellulose 
  becomes 
  less, 
  according 
  to 
  the 
  analytical 
  

   results 
  of 
  Albahary, 
  This 
  last 
  named 
  feature 
  is 
  the 
  reverse 
  of 
  

   that 
  in 
  stems 
  or 
  vegetative 
  tissues 
  in 
  which 
  the 
  cell 
  walls 
  become 
  

   heavier 
  and 
  more 
  indurated 
  with 
  progressive 
  development. 
  

  

  The 
  above 
  conditions 
  in 
  the 
  fruits 
  are 
  fully 
  sustained 
  by 
  the 
  

   following 
  set 
  of 
  swelling 
  reactions, 
  which 
  are 
  entirely 
  characteristic 
  

   of 
  a 
  pentosan-protein 
  colloid 
  high 
  in 
  mucilages 
  of 
  the 
  first 
  group, 
  

  

  w 
  

  

  Swelling 
  of 
  radial 
  slices 
  of 
  growing 
  fruits 
  25-35 
  ivim. 
  

  

  in 
  diaivieter 
  

  

  Propionic 
  acid 
  

  

  O.OlM 
  i 
  10% 
  

  

  Alanine 
  Phenyl-alanine 
  GlycocoU 
  

  

  25% 
  

  

  Water 
  

  

  25% 
  I 
  25% 
  I 
  21% 
  

  

  In 
  a 
  later 
  stage 
  of 
  the 
  fruits 
  when 
  the 
  skin 
  is 
  turning 
  yellow, 
  

  

  r 
  

  

  the 
  salt 
  content 
  amounts 
  to 
  10 
  per 
  cent 
  of 
  the 
  dry 
  weight 
  and 
  the 
  

   acidity 
  is 
  such 
  that 
  the 
  sap 
  has 
  hydrogen 
  ion 
  concentration 
  of 
  a 
  

   PH 
  value 
  = 
  4, 
  while 
  the 
  albumins 
  have 
  decreased/ 
  The 
  results 
  

   of 
  a 
  set 
  of 
  swellings 
  are 
  as 
  follows:* 
  

  

  Propionic 
  acid 
  Alanine 
  

  

  Phenyl-alanine 
  I 
  Glycocoll 
  

  

  Water 
  

  

  o.oiM 
  .! 
  16 
  I 
  15.5 
  i 
  II 
  

  

  15 
  I 
  15 
  

  

  * 
  Cuhn, 
  E. 
  J.. 
  J. 
  Gross 
  & 
  O. 
  Johnson.^ 
  The 
  isoelectric 
  points 
  of 
  the 
  proteins 
  in 
  

  

  Gen 
  

  

  1019. 
  

  

  