﻿86 
  Dr. 
  W. 
  B. 
  Bottomley. 
  The 
  Effect 
  of 
  Nitrogen-fixing 
  

  

  not 
  unreasonable 
  to 
  suppose 
  that 
  a 
  similar 
  result 
  might 
  he 
  attained 
  in 
  

   ordinary 
  water-culture 
  experiments 
  by 
  natural 
  bacterial 
  contamination, 
  which 
  

   is 
  almost 
  unavoidable 
  unless 
  the 
  most 
  scrupulous 
  care 
  be 
  taken 
  to 
  ensure 
  the 
  

   sterility 
  of 
  the 
  solutions 
  and 
  to 
  change 
  them 
  frequently. 
  It 
  should 
  be 
  

   pointed 
  out 
  that 
  the 
  gelatinous 
  growth 
  of 
  Azotobacter 
  contained 
  96 
  68 
  per 
  

   cent, 
  of 
  moisture, 
  so 
  that 
  the 
  addition 
  of 
  this 
  material 
  in 
  the 
  proportion 
  of 
  

   1 
  grm. 
  to 
  1,000 
  c.c. 
  of 
  solution 
  represents 
  only 
  33 
  - 
  2 
  parts 
  of 
  dry 
  substance 
  

   per 
  million, 
  containing 
  29 
  parts 
  of 
  organic 
  matter. 
  Tbis 
  quantity 
  could 
  

   quite 
  conceivably 
  be 
  supplied 
  by 
  bacterial 
  and 
  algal 
  contamination, 
  and 
  it 
  is 
  

   interesting 
  in 
  this 
  connection 
  to 
  point 
  out 
  that 
  it 
  has 
  been 
  frequently 
  

   observed 
  that 
  a 
  more 
  luxuriant 
  growth 
  is 
  obtained 
  in 
  water-culture 
  experi- 
  

   ments 
  when 
  the 
  solutions 
  become 
  contaminated 
  with 
  green 
  alga?. 
  

  

  Effect 
  of 
  Nucleic 
  Acid 
  Derivatives. 
  

  

  It 
  was 
  not 
  to 
  be 
  expected, 
  however, 
  that 
  the 
  whole 
  of 
  the 
  effect 
  of 
  the 
  

   bacterised 
  peat 
  extract 
  was 
  to 
  be 
  attributed 
  to 
  the 
  products 
  of 
  these 
  nitrogen- 
  

   fixing 
  bacteria 
  ; 
  and 
  since 
  the 
  effect 
  of 
  this 
  organic 
  extract 
  was 
  most 
  marked 
  

   upon 
  the 
  nuclei 
  of 
  the 
  young 
  developing 
  plants, 
  it 
  was 
  suggested 
  that 
  some 
  

   nuclear 
  constituent, 
  present 
  in 
  the 
  peat 
  and 
  rendered 
  available 
  during 
  the 
  

   process 
  of 
  " 
  bacterisation," 
  might 
  be 
  partially 
  responsible 
  for 
  the 
  results 
  

   obtained. 
  

  

  It 
  has 
  already 
  been 
  shown* 
  that 
  on 
  extracting 
  raw 
  peat 
  with 
  dilute 
  

   alkalies 
  and 
  removing 
  the 
  "humic 
  acids." 
  by 
  suitable 
  means, 
  certain 
  nucleic 
  

   acid 
  derivatives 
  can 
  be 
  obtained 
  ; 
  and 
  that 
  by 
  extracting 
  the 
  peat 
  repeatedly 
  

   with 
  a 
  1 
  per 
  cent, 
  solution 
  of 
  sodium 
  bicarbonate, 
  these 
  same 
  nucleic 
  acid 
  

   derivatives 
  are 
  obtained, 
  but 
  the 
  " 
  humic 
  acids 
  " 
  are 
  not 
  dissolved, 
  so 
  that 
  the 
  

   trouble 
  of 
  removing 
  these 
  latter 
  substances 
  is 
  avoided. 
  The 
  nucleic 
  acid 
  

   derivatives 
  thus 
  obtained 
  consist 
  generally 
  of 
  an 
  adenine-uracil 
  dinucleotide 
  

   and 
  two 
  mononucleotides 
  — 
  a 
  guanine 
  and 
  a 
  cytosine 
  mononucleotide. 
  The 
  

   dinucleotide 
  can 
  be 
  precipitated 
  from 
  the 
  sodium 
  bicarbonate 
  extract, 
  after 
  

   concentration 
  in 
  vacuo, 
  by 
  an 
  excess 
  of 
  absolute 
  alcohol 
  following 
  the 
  addition 
  

   of 
  sodium 
  acetate 
  and 
  hydrochloric 
  acid 
  to 
  the 
  extract. 
  A 
  flocculent 
  precipi- 
  

   tate 
  is 
  obtained, 
  which 
  settles 
  after 
  about 
  24 
  hours 
  to 
  a 
  fine 
  powder, 
  and 
  this 
  

   can 
  be 
  filtered 
  off 
  and 
  washed 
  with 
  absolute 
  alcohol. 
  The 
  two 
  mononucleo- 
  

   tides 
  remain 
  in 
  the 
  filtrate. 
  

  

  In 
  order 
  to 
  test 
  the 
  effect 
  of 
  these 
  various 
  substances 
  on 
  the 
  growth 
  of 
  

   Lemna 
  minor, 
  a 
  weighed 
  quantity 
  of 
  peat 
  was 
  repeatedly 
  extracted 
  with 
  

   successive 
  portions 
  of 
  a 
  1 
  per 
  cent, 
  solution 
  of 
  sodium 
  bicarbonate 
  until 
  the 
  

   extract 
  was 
  no 
  longer 
  coloured. 
  The 
  combined 
  extracts, 
  after 
  carefully 
  

   * 
  Bottoniley, 
  W. 
  B., 
  ' 
  Boy. 
  Soc. 
  Proc.,' 
  B, 
  vol. 
  90, 
  pp. 
  39-44 
  (1917). 
  

  

  