﻿426 
  Rusk: 
  Protoplasmic 
  streaming 
  

  

  0.0003 
  N 
  to 
  0.0015 
  N 
  stimulates 
  Skrigmatocystis 
  nigra 
  with 
  the 
  

   result 
  that 
  less 
  nitrogen 
  is 
  fixed 
  by 
  the 
  fungus. 
  The 
  greatest 
  

   stimulation 
  was 
  obtained 
  by 
  solutions 
  from 
  0.0003 
  N 
  to 
  o.ooi 
  N 
  

   (see 
  Latham, 
  4). 
  

  

  For 
  the 
  test 
  solutions 
  in 
  this 
  work 
  Merck's 
  reagent 
  zinc 
  sulphate 
  

   was 
  used 
  and 
  was 
  kept 
  sealed 
  with 
  paraffin 
  when 
  not 
  in 
  use. 
  

   It 
  was 
  weighed 
  out 
  on 
  a 
  delicate 
  Becker 
  balance, 
  and 
  a 
  o.i 
  iV 
  

   stock 
  solution 
  made. 
  For 
  most 
  of 
  the 
  work 
  wnth 
  Elodea, 
  the 
  

  

  * 
  

  

  stock 
  solution 
  was 
  made 
  up 
  in 
  distilled 
  water; 
  but 
  for 
  part 
  of 
  this 
  

   work, 
  and 
  for 
  all 
  of 
  that 
  with 
  Chara, 
  double 
  distilled 
  water 
  was 
  used. 
  

   Dilutions 
  were 
  made 
  from 
  this 
  stock 
  solution 
  as 
  needed. 
  For 
  all 
  

   measurements 
  accurately 
  graduated 
  flasks 
  and 
  pipettes 
  were 
  

   used. 
  Filtered 
  tap 
  water 
  was 
  considered 
  to 
  be 
  a 
  better 
  medium 
  

   for 
  controls 
  than 
  distilled 
  water, 
  since 
  it 
  is 
  much 
  more 
  like 
  the 
  

  

  ■ 
  

  

  medium 
  in 
  which 
  these 
  plants 
  naturally 
  live. 
  Hence 
  tap 
  water, 
  

   filtered 
  through 
  a 
  Berkefeld 
  filter, 
  was 
  used 
  for 
  controls; 
  it 
  was 
  

   also 
  used 
  for 
  making 
  dilutions 
  from 
  the 
  stock 
  solution 
  of 
  sine 
  zul- 
  

   phate, 
  so 
  as 
  to 
  make 
  the 
  test 
  solutions 
  differ 
  from 
  the 
  control 
  only 
  

   in 
  the 
  presence 
  of 
  the 
  zinc 
  sulphate. 
  

  

  A 
  Gtock 
  supply 
  of 
  the 
  plants 
  was 
  kept 
  in 
  the 
  greenhouse 
  In 
  

   jars 
  with 
  snails. 
  Small 
  amounts 
  were 
  brought 
  into 
  the 
  laboratory 
  

   from 
  time 
  to 
  time, 
  and 
  kept 
  in 
  filtered 
  water. 
  Specimens 
  put 
  into 
  

   test 
  solutions 
  were 
  taken 
  directly 
  from 
  filtered 
  water. 
  The 
  

   temperature 
  of 
  the 
  water 
  or 
  solution 
  was 
  between 
  19° 
  and 
  25^ 
  C. 
  

  

  ■ 
  r 
  

  

  at 
  the 
  beginning 
  of 
  all 
  the 
  observations; 
  at 
  the 
  beginning 
  of 
  all 
  

   but 
  a 
  very 
  few 
  it 
  was 
  between 
  21° 
  and 
  24^ 
  C- 
  The 
  light 
  used 
  for 
  

   all 
  the 
  observations 
  was 
  that 
  of 
  a 
  60-watt 
  lamp 
  coming 
  to 
  the 
  

   mirror 
  of 
  the 
  microscope 
  through 
  an 
  ammonia 
  copper 
  sulphate 
  

   globe. 
  

  

  For 
  most 
  of 
  the 
  work 
  with 
  Elodea 
  the 
  following 
  method 
  was 
  

   used: 
  Several 
  healthy 
  looking 
  leaves 
  were 
  taken 
  from 
  the 
  same 
  

   region 
  of 
  the 
  same 
  stem, 
  and 
  placed, 
  some 
  In 
  a 
  separate 
  dish 
  of 
  

   filtered 
  water, 
  and 
  some 
  in 
  a 
  similar 
  dish 
  containing 
  about 
  an 
  

   equal 
  amount 
  of 
  the 
  zinc 
  sulphate 
  solution. 
  One 
  of 
  the 
  leaves 
  

   from 
  the 
  zinc 
  sulphate 
  solution 
  was 
  then 
  mounted 
  on 
  a 
  slide 
  in 
  

   some 
  of 
  the 
  same 
  solution, 
  and 
  observations 
  were 
  made 
  on 
  from 
  

   three 
  to 
  five 
  of 
  Its 
  cells. 
  This 
  was 
  done 
  within 
  an 
  hour 
  and 
  a 
  half 
  

   of 
  the 
  time 
  of 
  starting. 
  Then 
  a 
  leaf 
  from 
  the 
  dish 
  of 
  filtered 
  

  

  