﻿522' 
  EEPOET 
  OF 
  COMMISSIOISrER 
  OF 
  FISH 
  AIN'D 
  FISHERIES. 
  

  

  5. 
  These 
  rooted 
  aquatics 
  are 
  important 
  contributors 
  to 
  the 
  plankton 
  

   food 
  supply, 
  because 
  when 
  living- 
  tliey 
  org-anize 
  matter 
  that 
  may 
  be 
  

   used 
  as 
  food 
  and 
  in 
  death 
  the}" 
  yield 
  important 
  salts 
  and 
  organic 
  sub- 
  

   stances 
  to 
  the 
  water. 
  Artari 
  (1901) 
  finds 
  that 
  certain 
  alg^e 
  prefer 
  

   org-anic 
  nourishment, 
  and 
  it 
  is 
  quite 
  possible 
  that 
  many 
  of 
  the 
  forms 
  

   so 
  abundant 
  on 
  wounded 
  and 
  deca3nng- 
  portions 
  of 
  the 
  larger 
  plants 
  

   derive 
  considerable 
  nourishment 
  therefrom. 
  

  

  ECONOMIC 
  SIGNIFICANCE 
  OF 
  RESULTS. 
  

  

  The 
  foregoing 
  investigation 
  ma}" 
  be 
  regarded 
  as 
  a 
  step 
  in 
  the 
  

   endeavor 
  to 
  ascertain 
  those 
  factors 
  which 
  determine 
  the 
  quantity 
  of 
  

   food 
  fish 
  occurring 
  in 
  the 
  Great 
  Lakes. 
  From 
  the 
  introduction 
  it 
  

   appears 
  that 
  the 
  hirger 
  plants 
  are 
  already 
  credited 
  with 
  favoring 
  the 
  

   increase 
  of 
  fish 
  food 
  b}' 
  protecting 
  the 
  bottom 
  soil 
  against 
  wave 
  action, 
  

   and 
  by 
  affording 
  a 
  shelter 
  for 
  many 
  small 
  animals 
  and 
  3'oung 
  fish, 
  as 
  

   well 
  as 
  b}"- 
  acting 
  as 
  mechanical 
  supports 
  for 
  the 
  alga?, 
  wdiicli 
  are 
  used 
  

   as 
  food 
  by 
  many 
  animals. 
  If 
  the 
  observations 
  recorded 
  in 
  this 
  paper 
  

   are 
  correct, 
  there 
  must 
  now 
  be 
  definitel}' 
  assigned 
  to 
  the 
  rooted 
  aquatic 
  

   plants 
  a 
  nutritive 
  role 
  of 
  which 
  they 
  have 
  hitherto 
  been 
  only 
  suspected. 
  

   The 
  roots 
  of 
  the 
  plants 
  investigated 
  are 
  true 
  absorbing 
  organs, 
  taking 
  

   from 
  the 
  soil 
  valuable 
  salts 
  that 
  would 
  otherwise 
  be 
  retained 
  by 
  it, 
  and 
  

   furnishing 
  these 
  salts 
  to 
  the 
  growing 
  stems 
  and 
  leaves 
  for 
  the 
  build- 
  

   ing 
  up 
  of 
  more 
  plant 
  tissue. 
  So 
  dependent 
  upon 
  the 
  soil 
  are. 
  these 
  

   rooted 
  aquatics 
  that 
  they 
  can 
  not 
  survive 
  a 
  growing 
  season 
  if 
  deprived 
  

   of 
  it. 
  Thus, 
  instead 
  of 
  taking 
  their 
  mineral 
  food 
  exclusively 
  from 
  

   the 
  water, 
  as 
  formerly 
  supposed, 
  and 
  so 
  temporarily 
  withdrawing 
  val- 
  

   uable 
  salts 
  from 
  the 
  water, 
  these 
  rooted 
  aquatics 
  take 
  their 
  food 
  from 
  

   the 
  soil 
  and 
  organize 
  it 
  into 
  vegetable 
  matter. 
  Upon 
  the 
  decay 
  of 
  the 
  

   vegetable 
  matter 
  this 
  food 
  material 
  is 
  believed 
  to 
  pass 
  into 
  solution 
  in 
  

   the 
  water. 
  It 
  should 
  there 
  nourish 
  the 
  plankton 
  alga?, 
  which, 
  in 
  their 
  

   turn, 
  are 
  used 
  as 
  food 
  by 
  the 
  smaller 
  animal 
  forms, 
  and 
  these 
  in 
  turn 
  

   are 
  fed 
  upon 
  b}" 
  larger 
  animals 
  and 
  by 
  fishes. 
  

  

  In 
  western 
  Lake 
  Erie, 
  where 
  large 
  areas 
  of 
  the 
  substratum 
  in 
  coves 
  

   and 
  bays 
  are 
  occupied 
  by 
  dense 
  fields 
  of 
  plants 
  (aquatic 
  meadows), 
  the 
  

   changing 
  winds 
  often 
  create 
  currents 
  which 
  carry 
  out 
  into 
  the 
  lake 
  

   large 
  quantities 
  of 
  plant 
  debris. 
  This 
  during 
  the 
  period 
  of 
  slow 
  oxi- 
  

   dation 
  represents 
  so 
  much 
  organized 
  matter 
  available 
  for 
  plankton 
  

   nutrition, 
  and 
  in 
  final 
  deca}" 
  yields 
  important 
  mineral 
  salts 
  to 
  the 
  water, 
  

   thus 
  adding 
  to 
  the 
  food 
  supply 
  of 
  the 
  plant 
  plankton. 
  

  

  That 
  there 
  is 
  a 
  direct 
  relation 
  between 
  the 
  quantity 
  of 
  food 
  fish 
  and 
  

   the 
  quantity 
  of 
  plankton 
  has 
  long 
  been 
  believed. 
  Ilecently 
  Kofoid 
  

   (1903) 
  has 
  produced 
  quantitative 
  evidence 
  to 
  shoAV 
  that 
  in 
  the 
  Illinois 
  

   River 
  and 
  its 
  back 
  w^aters 
  such 
  a 
  relation 
  exists, 
  in 
  the 
  sense 
  that 
  

   "there 
  is 
  in 
  general 
  a 
  correspondence 
  between 
  plankton 
  production 
  

   and 
  the 
  product 
  of 
  the 
  fisheries, 
  in 
  that 
  the 
  direction 
  of 
  movement 
  in 
  

  

  