﻿The 
  effect 
  of 
  zinc 
  sulphate 
  

  

  Hester 
  M. 
  Rusk 
  

  

  (with 
  two 
  text 
  figures) 
  

  

  In 
  view 
  of 
  the 
  fact 
  that 
  metalHc 
  poisons 
  in 
  minimal 
  doses 
  

   stimulate 
  the 
  metabolic 
  activity 
  of 
  many 
  plants, 
  as 
  has 
  been 
  

   shown 
  by 
  the 
  researches 
  of 
  many 
  workers, 
  it 
  seemed 
  a 
  matter 
  of 
  

   interest 
  to 
  determine 
  whether 
  any 
  ocular 
  evidence 
  of 
  excitation 
  

   could 
  be 
  observed 
  in 
  individual 
  cells. 
  Of 
  all 
  the 
  poisons 
  employed 
  

   we 
  have 
  the 
  most 
  data 
  regarding 
  the 
  effect 
  of 
  zinc 
  sulphate, 
  and 
  

   in 
  this 
  work 
  the 
  observations 
  w^ere 
  limited 
  almost 
  entirely 
  to 
  the 
  

   action 
  of 
  that 
  salt. 
  A 
  few 
  observations 
  were 
  made 
  with 
  other 
  

   substances, 
  such 
  as 
  cobalt 
  nitrate 
  and 
  sulphuric 
  acid, 
  but 
  without 
  

   very 
  definite 
  results. 
  ' 
  The 
  most 
  convenient 
  visible 
  reaction 
  to 
  

   observe 
  is 
  the 
  effect 
  on 
  the 
  rotation 
  of 
  protoplasm 
  in 
  active 
  cells. 
  

   For 
  this 
  purpose 
  cells 
  of 
  the 
  leaf 
  of 
  Elodea 
  canadensis 
  and 
  cells 
  

   from 
  an 
  uncorticated 
  Chara 
  were 
  taken. 
  

  

  While 
  the 
  literature 
  is 
  rich 
  regarding 
  the 
  action 
  of 
  metallic 
  

   poisons 
  on 
  the 
  stimulation 
  of 
  growth 
  and 
  certain 
  of 
  the 
  metabolic 
  

   processes 
  concerned 
  in 
  the 
  use 
  of 
  nutrient 
  material, 
  there 
  is 
  not 
  a 
  

   large 
  amount 
  on 
  the 
  effect 
  of 
  irritant 
  substances 
  on 
  the 
  rate 
  of 
  

   streaming. 
  Ewart 
  (1, 
  p. 
  87) 
  says, 
  *'all 
  concentrations 
  [of 
  metallic 
  

   poisons] 
  sufficient 
  to 
  produce 
  any 
  effect 
  cause 
  from 
  the 
  outset 
  

   progressive 
  retardation," 
  He 
  cites 
  only 
  experiments 
  with 
  sodium 
  

   chloride 
  (0.1-0.5 
  P^i" 
  cent) 
  and 
  cupric 
  sulphate 
  (0.5-10 
  per 
  cent), 
  

   however. 
  

  

  With 
  regard 
  to 
  the 
  effect 
  of 
  metallic 
  poisons 
  on 
  other 
  functions 
  

   of 
  plants 
  it 
  has 
  been 
  found 
  (i) 
  That 
  zinc 
  sulphate 
  in 
  concentra- 
  

   tions 
  from 
  0.000125 
  ^ 
  t^ 
  0.002 
  N 
  stimulates 
  the 
  growth 
  of 
  Asper- 
  

   gillus 
  niger 
  and 
  Penicillium 
  glaucmn, 
  resulting 
  in 
  an 
  increase 
  of 
  

   dry 
  weight. 
  The 
  greatest 
  stimulation 
  was 
  obtained 
  by 
  a 
  con- 
  

  

  centration 
  of 
  

  

  000 
  

  

  0005 
  N 
  

  

  (2). 
  That 
  the 
  same 
  concentrations 
  of 
  zinc 
  sulphate 
  stimulate 
  the 
  

   same 
  fungi, 
  causing 
  them 
  to 
  make 
  a 
  more 
  economical 
  use 
  of 
  sugar. 
  

   The 
  greatest 
  stimulation 
  was 
  obtained 
  by 
  0.00025 
  N 
  (see 
  

   Richards, 
  3). 
  (3) 
  That 
  zinc 
  sulphate 
  in 
  concentrations 
  from 
  

  

  425 
  

  

  