﻿CONTRIBUTIONS 
  TO 
  THE 
  BIOLOGY 
  OF 
  THE 
  GREAT 
  LAKES. 
  

  

  THE 
  BIOLOGICAL 
  RELATION 
  OF 
  AQUATIC 
  PLANTS 
  TO 
  THE 
  

   SUBSTRATUM. 
  

  

  By 
  Raymond 
  H. 
  Pond. 
  

  

  INTRODUCTION. 
  

  

  This 
  investigation 
  was 
  undertaken 
  at 
  the 
  suggestion 
  of 
  Prof. 
  Jacob 
  

   Reighard, 
  in 
  charge 
  of 
  the 
  biological 
  survey 
  of 
  the 
  Great 
  Lakes 
  under 
  

   the 
  auspices 
  of 
  the 
  United 
  States 
  Fish 
  Commission. 
  It 
  was 
  carried 
  on 
  

   during 
  three 
  j^ears, 
  chiefly 
  in 
  the 
  summer, 
  parti}" 
  at 
  Put-in 
  Ba}', 
  Ohio, 
  

   and 
  partly 
  at 
  Ann 
  Arbor, 
  Mich., 
  under 
  the 
  direction 
  of 
  Prof. 
  F, 
  C. 
  

   Newcombe, 
  of 
  the 
  University 
  of 
  Michigan, 
  to 
  whom 
  1 
  am 
  indebted 
  for 
  

   constant 
  guidance. 
  To 
  Mr. 
  A. 
  J. 
  Pieters, 
  of 
  the 
  U. 
  S. 
  Department 
  

   of 
  Agriculture, 
  I 
  am 
  indebted 
  for 
  the 
  use 
  of 
  his 
  A^ery 
  complete 
  bibli- 
  

   ography 
  of 
  aquatic 
  plants. 
  The 
  discussion 
  of 
  the 
  papers 
  by 
  Forel, 
  

   Hoppe-Seyler, 
  Seligo, 
  and 
  Stockmayer, 
  constituting 
  the 
  introduction 
  

   as 
  well 
  as 
  the 
  larger 
  portion 
  of 
  the 
  chapter 
  on 
  economic 
  significance 
  of 
  

   results, 
  is 
  from 
  the 
  pen 
  of 
  Prof. 
  Jacob 
  Reighard. 
  

  

  One 
  of 
  the 
  objects 
  of 
  the 
  biological 
  survey 
  of 
  the 
  Great 
  Lakes 
  was 
  

   to 
  ascertain 
  the 
  factors 
  which 
  determine 
  the 
  quantity 
  of 
  food 
  fish 
  it 
  is 
  

   possible 
  for 
  these 
  lakes 
  to 
  support. 
  To 
  this 
  end 
  it 
  was 
  necessary 
  to 
  

   study 
  not 
  only 
  the 
  fishes 
  themselves, 
  but 
  all 
  forms 
  of 
  animal 
  and 
  plant 
  

   life 
  in 
  the 
  lakes, 
  for 
  upon 
  these, 
  directly 
  or 
  indirectly, 
  the 
  fishes 
  depend. 
  

  

  That 
  the 
  larger 
  aquatic 
  plants 
  play 
  an 
  important 
  part 
  in 
  the 
  biology 
  

   of 
  fresh 
  water 
  has 
  been 
  long 
  recognized, 
  and 
  at 
  least 
  two 
  roles 
  have 
  

   been 
  assigned 
  to 
  them. 
  The 
  first 
  of 
  these 
  is 
  mechanical. 
  Often 
  the 
  

   plants 
  growing 
  submerged 
  are 
  so 
  abundant 
  as 
  to 
  cover 
  the 
  bottom. 
  

   Their 
  fine 
  rootlets 
  give 
  to 
  the 
  bottom 
  soil 
  greater 
  coherence, 
  while 
  

   their 
  stems 
  and 
  leaves 
  protect 
  it 
  from 
  the 
  mechanical 
  action 
  of 
  the 
  

   waves. 
  Such 
  plants, 
  moreover, 
  form 
  aquatic 
  meadows 
  in 
  whose 
  dense 
  

   growth 
  multitudes 
  of 
  small 
  animals 
  and 
  ,young 
  fish 
  find 
  shelter 
  and 
  

   concealment 
  from 
  pursuing 
  enemies. 
  Some 
  fishes 
  select 
  these 
  meadows 
  

   as 
  localities 
  in 
  which 
  to 
  lay 
  their 
  eggs, 
  and 
  the 
  minute 
  plant 
  and 
  animal 
  

  

  485 
  

  

  