﻿524 
  KEPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  their 
  decay. 
  So 
  far 
  as 
  concerns 
  vegetation 
  like 
  this, 
  his 
  conclusions 
  

   are 
  precisely 
  those 
  which 
  seem 
  necessaril}^ 
  to 
  follow 
  from 
  the 
  experi- 
  

   mental 
  results 
  recorded 
  in 
  this 
  paper. 
  

  

  In 
  contrast 
  to 
  Flag- 
  Lake, 
  however, 
  are 
  Dog-lish 
  and 
  Quiver 
  lakes, 
  

   which 
  are 
  tilled 
  with 
  a 
  rich 
  growth 
  of 
  submerged 
  vegetation. 
  This 
  

   "consists 
  in 
  the 
  main 
  of 
  CeratopliyUum^ 
  with 
  an 
  admixture 
  of 
  Elodea 
  

   and 
  P<>tainogetonio'^^x<\ 
  the 
  margin" 
  (Kofoid, 
  1908, 
  p. 
  244). 
  It 
  is 
  this 
  

   sort 
  of 
  submerged 
  non-rooted 
  vegetation 
  which 
  Kofoid 
  shows 
  to 
  be 
  

   unfavorable 
  to 
  an 
  abundant 
  phxnkton, 
  so 
  that 
  lakes 
  which 
  contain 
  it 
  

   and 
  which 
  he 
  calls 
  vegetation-rich 
  have 
  less 
  plankton 
  than 
  otherwise 
  

   similar 
  lakes 
  which 
  are 
  without 
  it. 
  The 
  conclusion 
  that 
  an 
  abundance 
  

   of 
  submerged 
  vegetation 
  is 
  inimical 
  to 
  the 
  development 
  of 
  a 
  rich 
  plank- 
  

   ton 
  seems 
  at 
  first 
  sight 
  to 
  be 
  at 
  variance 
  with 
  the 
  conclusions 
  reached 
  

   in 
  this 
  paper, 
  and 
  Kofoid's 
  general 
  formula, 
  "The 
  amount 
  of 
  plankton 
  

   produced 
  b}'^ 
  bodies 
  of 
  fresh 
  water 
  is, 
  other 
  things 
  l)eing 
  equal, 
  in 
  some 
  

   inverse 
  ratio 
  proportional 
  to 
  the 
  amount 
  of 
  its 
  gross 
  aquatic 
  vegetation 
  

   of 
  the 
  submerged 
  sort,'' 
  is 
  certainly 
  not 
  in 
  accordance 
  with 
  these 
  con- 
  

   clusions. 
  Yet 
  the 
  apparent 
  contradiction 
  between 
  his 
  results 
  and 
  those 
  

   here 
  recorded 
  disappears 
  when 
  it 
  is 
  remembered 
  that 
  the 
  submerged 
  

   vegetation 
  to 
  which 
  he 
  has 
  reference 
  is 
  composed 
  chiefly 
  of 
  CendophyJ- 
  

   lum^ 
  and 
  that 
  CeratoplajUum 
  is 
  a 
  rootless 
  form, 
  which 
  undou})tedly 
  

   draws 
  its 
  food 
  supply 
  from 
  the 
  water 
  only. 
  It 
  thus 
  competes 
  with 
  the 
  

   phytoplankton 
  for 
  food, 
  and 
  an 
  abundant 
  growth 
  of 
  it 
  is 
  necessarily 
  

   correlated 
  with 
  a 
  scant 
  growth 
  of 
  phytoplaidvton. 
  On 
  the 
  other 
  hand, 
  

   the 
  submerged 
  vegetation 
  considered 
  in 
  this 
  paper 
  is 
  rooted; 
  it 
  draws 
  

   its 
  mineral 
  nourishment 
  from 
  the 
  soil 
  and 
  in 
  decay 
  yields 
  it 
  to 
  the 
  

   water. 
  It 
  does 
  not, 
  therefore, 
  compete 
  with 
  the 
  phytoplankton, 
  and 
  

   its 
  presence 
  is, 
  from 
  a 
  nutritive 
  standpoint, 
  favorable 
  to 
  the 
  develop- 
  

   ment 
  of 
  phytoplankton. 
  

  

  From 
  the 
  standpoint 
  of 
  nutritive 
  relations, 
  then, 
  all 
  vegetation 
  of 
  

   fresh 
  waters 
  may 
  be 
  divided 
  into 
  two 
  classes: 
  (1) 
  The 
  rooted 
  vegetation, 
  

   which 
  may 
  be 
  either 
  emergent 
  (e. 
  g. 
  , 
  Scirjms) 
  or 
  submerged 
  (e. 
  g. 
  , 
  YaUis- 
  

   7ierla, 
  etc.), 
  and 
  which 
  includes 
  nearly 
  all 
  the 
  gross 
  aquatic 
  plants. 
  

   Of 
  these 
  it 
  may 
  be 
  said 
  that 
  they 
  draw 
  their 
  mineral 
  food 
  from 
  

   the 
  soil 
  and 
  are 
  thus 
  favorable 
  to 
  the 
  growth 
  of 
  the 
  phytoplankton. 
  

   (2) 
  Nonrooted 
  vegetation, 
  consisting 
  of 
  (a) 
  gross, 
  nonrooted 
  phanero- 
  

   gams, 
  made 
  up 
  almost 
  wholly 
  in 
  temperate 
  regions 
  of 
  CeratophyUimi 
  

   and 
  the 
  Lemnacex^ 
  and 
  (b) 
  minute, 
  nonrooted 
  crj'ptogams, 
  which 
  are 
  

   mostly 
  members 
  of 
  the 
  phytoplankton. 
  All 
  these 
  nonrooted 
  plants 
  

   draw 
  their 
  mineral 
  food 
  from 
  the 
  water, 
  and 
  hence 
  the 
  two 
  subdivi- 
  

   sions, 
  the 
  gross 
  and 
  the 
  microscopic, 
  compete 
  with 
  one 
  another, 
  so 
  

   that 
  an 
  abundance 
  of 
  nonrooted 
  gross 
  plants 
  results 
  in 
  a 
  reduced 
  

   plankton. 
  Kofoid's 
  formula 
  modified 
  to 
  bring 
  it 
  into 
  accord 
  with 
  all 
  

   the 
  facts 
  would 
  read, 
  "The 
  amount 
  of 
  plankton 
  produced 
  by 
  bodies 
  

   of 
  fresh 
  water 
  is, 
  other 
  things 
  being 
  equal, 
  in 
  some 
  inverse 
  ratio 
  pro- 
  

   portional 
  to 
  the 
  amount 
  of 
  its 
  gross 
  nonrooted 
  vegetation 
  and 
  in 
  some 
  

  

  