﻿'92 
  Dr. 
  W. 
  B. 
  Bottomley. 
  The 
  Effect 
  of 
  Nitrogen- 
  fixing 
  

  

  treated 
  precisely 
  as 
  in 
  the 
  preceding 
  experiments 
  with 
  regard 
  to 
  the 
  exclusion 
  

   of 
  light 
  from 
  bottom 
  and 
  sides 
  and 
  protection 
  from 
  dust. 
  The 
  solutions 
  

   were 
  changed 
  twice 
  weekly, 
  and 
  the 
  plants 
  counted 
  once 
  weekly, 
  one 
  half 
  of 
  

   each 
  dish 
  being 
  rejected 
  at 
  the 
  weekly 
  counting 
  when 
  necessary. 
  The 
  

   numbers 
  obtained 
  are 
  shown 
  in 
  the 
  Table 
  IV. 
  

  

  Estimations 
  of 
  the 
  dry 
  weights 
  of 
  the 
  fractions 
  discarded 
  at 
  the 
  weekly 
  

   countings 
  were 
  made 
  at 
  the 
  end 
  of 
  the 
  third, 
  fifth, 
  and 
  eighth 
  weeks 
  respec- 
  

   tively, 
  with 
  the 
  following 
  results 
  : 
  — 
  

  

  Table 
  V. 
  

  

  Series 
  No. 
  

  

  At 
  beginning. 
  

  

  3rd 
  week. 
  

  

  5th 
  week. 
  

  

  8th. 
  week. 
  

  

  I 
  

  

  10 
  -9 
  

  

  10-8 
  

  

  9-9 
  

  

  6-5 
  

  

  II 
  

  

  10-9 
  

  

  12-2 
  

  

  16 
  -0 
  

  

  18-5 
  

  

  III 
  

  

  10 
  -9 
  

  

  12 
  -5 
  

  

  15 
  -9 
  

  

  19 
  -1 
  

  

  These 
  figures 
  indicate 
  that 
  Bacillus 
  radicicola 
  is 
  quite 
  as 
  effective 
  as 
  

   Azotobacter 
  chroococcum 
  in 
  promoting 
  the 
  growth 
  of 
  Lemna 
  plants. 
  

  

  Effect 
  of 
  the 
  Ash 
  Constituents. 
  

  

  In 
  all 
  the 
  experiments 
  hitherto 
  described, 
  it 
  has 
  been 
  assumed 
  that 
  it 
  is 
  

   the 
  organic 
  constituents 
  of 
  the 
  additions 
  to 
  the 
  nutrient 
  solutions 
  which 
  

   have 
  brought 
  about 
  the 
  large 
  increases 
  in 
  growth. 
  There 
  was 
  the 
  possi- 
  

   bility, 
  however, 
  that 
  minute 
  quantities 
  of 
  certain 
  inorganic 
  substances 
  

   present 
  in 
  the 
  materials 
  might 
  function 
  as 
  activators, 
  and 
  thus 
  account 
  for 
  

   the 
  results 
  obtained. 
  In 
  order 
  to 
  test 
  this, 
  fresh 
  quantities 
  of 
  the 
  crude 
  

   nucleic 
  acid 
  derivatives, 
  and 
  of 
  the 
  Azotobacter 
  growth 
  were 
  prepared 
  as 
  

   above 
  described, 
  in 
  May 
  of 
  1918, 
  and 
  each 
  was 
  divided 
  into 
  two 
  equal 
  parts. 
  

   One 
  half 
  of 
  each 
  was 
  carefully 
  evaporated 
  to 
  dryness 
  in 
  a 
  porcelain 
  dish 
  

   over 
  a 
  water 
  bath, 
  and 
  the 
  residue 
  completely 
  incinerated. 
  When 
  cold 
  the 
  

   ash 
  was 
  ground 
  to 
  a 
  fine 
  powder 
  with 
  a 
  little 
  water, 
  and 
  carefully 
  transferred 
  

   to 
  a 
  calibrated 
  stoppered 
  flask, 
  the 
  dish 
  being 
  rinsed 
  with 
  successive 
  small 
  

   quantities 
  of 
  conductivity 
  water, 
  which 
  were 
  added 
  to 
  the 
  flask. 
  The 
  

   whole 
  was 
  made 
  up 
  to 
  a 
  known 
  volume, 
  so 
  that 
  an 
  aliquot 
  portion 
  of 
  the 
  

   well-mixed 
  contents 
  could 
  be 
  taken, 
  representing 
  the 
  ash 
  from 
  a 
  known 
  

   weight 
  of 
  the 
  original 
  material 
  used. 
  

  

  Twenty-five 
  dishes 
  were 
  then 
  arranged 
  in 
  five 
  series 
  of 
  five 
  dishes 
  each, 
  

   and 
  all 
  contained 
  150 
  c.c. 
  of 
  Detmer's 
  solution. 
  Series 
  I, 
  containing 
  dishes 
  

   numbered 
  from 
  1 
  to 
  5, 
  constituted 
  the 
  control 
  series, 
  and 
  to 
  the 
  dishes 
  of 
  

  

  