﻿DELATION 
  OF 
  AQUATIC 
  PLANTS 
  TO 
  SUBSTKATUM. 
  523 
  

  

  both 
  is 
  iisiiall}' 
  the 
  same. 
  They 
  rise 
  or 
  fall 
  together." 
  The 
  argu- 
  

   ment 
  presented 
  by 
  Kofoid 
  will 
  not 
  be 
  critically 
  discussed 
  here. 
  

  

  In 
  view 
  of 
  the 
  results 
  obtained 
  in 
  this 
  investigation, 
  it 
  appears 
  

   highly 
  probable 
  that 
  through 
  the 
  mediation 
  of 
  the 
  attached 
  plants 
  the 
  

   abundant 
  mineral 
  salts 
  held 
  fixed 
  by 
  the 
  soil 
  become 
  available 
  for 
  

   the 
  nourishment 
  of 
  the 
  phytoplankton. 
  On 
  this 
  basis 
  it 
  is 
  possible 
  

   to 
  attribute 
  the 
  scarcit}^ 
  of 
  plankton 
  and 
  fish 
  in 
  some 
  waters 
  in 
  part 
  

   at 
  least 
  to 
  the 
  scarcity 
  of 
  the 
  larger, 
  rooted, 
  aquatic 
  plants. 
  Kofoid 
  

   (1903) 
  shows, 
  in 
  the 
  case 
  of 
  Flag 
  Lake, 
  that 
  an 
  abundant 
  rooted 
  vege- 
  

   tation 
  is 
  favorable 
  to 
  a 
  high 
  plankton 
  production. 
  In 
  the 
  other 
  lakes 
  

   examined 
  by 
  him 
  he 
  has 
  made 
  careful 
  measurements 
  of 
  the 
  plankton 
  

   at 
  frequent 
  intervals 
  for 
  a 
  period 
  of 
  five 
  years, 
  and 
  he 
  divides 
  these 
  

   lakes 
  into 
  two 
  groups 
  — 
  vegetation 
  rich, 
  which 
  contain 
  an 
  abundance 
  

   of 
  submerged 
  aquatic 
  plants, 
  and 
  vegetation 
  poor, 
  which 
  contain 
  but 
  

   little 
  submerged 
  aquatic 
  vegetation. 
  He 
  concludes 
  from 
  his 
  measure- 
  

   ments 
  of 
  the 
  plankton 
  that 
  the 
  vegetation-rich 
  lakes 
  produce 
  less 
  

   plankton 
  than 
  the 
  vegetation-poor 
  lakes. 
  He 
  says: 
  "This 
  relation 
  of 
  

   vegetation 
  to 
  plankton 
  may 
  be 
  formulated 
  as 
  follows: 
  The 
  amount 
  of 
  

   plankton 
  produced 
  by 
  bodies 
  of 
  fresh 
  water 
  is, 
  other 
  things 
  being 
  

   equal, 
  in 
  some 
  inverse 
  ratio 
  proportional 
  to 
  the 
  amount 
  of 
  its 
  gross 
  

   aquatic 
  vegetation 
  ot 
  the 
  submerged 
  sort."' 
  (Kofoid 
  1903, 
  p. 
  481, 
  

   footnote.) 
  The 
  relativel}' 
  small 
  amount 
  of 
  plankton 
  in 
  vegetation- 
  

   rich 
  lakes 
  Kofoid 
  attributes 
  to 
  a 
  number 
  of 
  factors. 
  In 
  part 
  it 
  is 
  due 
  

   to 
  the 
  fact 
  that 
  the 
  vegetation 
  shuts 
  out 
  the 
  heat 
  and 
  light 
  of 
  the 
  sun 
  

   and 
  thus 
  keeps 
  all 
  but 
  the 
  surface 
  la3'er 
  of 
  water 
  in 
  shade 
  and 
  at 
  low 
  

   temperature, 
  so 
  that 
  plankton 
  algge 
  do 
  not 
  develop 
  readily. 
  In 
  part 
  

   it 
  is 
  probably 
  to 
  be 
  attributed 
  to 
  the 
  presence 
  of 
  plankton-eating 
  ani- 
  

   mals 
  which 
  find 
  shelter 
  in 
  the 
  dense, 
  gross 
  vegetation. 
  Chiefly, 
  how- 
  

   ever, 
  he 
  attributes 
  it 
  to 
  the 
  fact 
  that 
  the 
  larger 
  aquatic 
  plants 
  take 
  

   from 
  the 
  water 
  and 
  utilize 
  in 
  their 
  growth 
  the 
  greater 
  part 
  of 
  the 
  

   available 
  food 
  materials. 
  Thus 
  plankton 
  vegetation 
  is 
  unable 
  to 
  

   develop 
  because 
  the 
  water 
  has 
  been 
  depleted 
  of 
  the 
  food 
  substances 
  

   necessary 
  for 
  its 
  nutrition. 
  Hence 
  the 
  development 
  of 
  an 
  abundance 
  

   of 
  submerged 
  aquatic 
  vegetation 
  results 
  in 
  a 
  diminished 
  plankton, 
  

   while 
  a 
  scant 
  submerged 
  vegetation 
  is 
  correlated, 
  other 
  conditions 
  

   being 
  the 
  same, 
  with 
  a 
  more 
  abundant 
  plankton, 
  

  

  ^Vhile 
  Kofoid 
  recognizes 
  in 
  the 
  case 
  of 
  Flag 
  Lake 
  that 
  an 
  abundant 
  

   rooted 
  vegetation 
  is 
  favorable 
  to 
  plankton 
  production, 
  he 
  points 
  out 
  

   that 
  this 
  vegetation 
  is 
  either 
  succulent 
  {Sagittaria., 
  Pontederia^ 
  JS^ym- 
  

   phsea,, 
  J^eliunho), 
  in 
  which 
  case 
  it 
  dies 
  down 
  and 
  decaj's 
  in 
  earh^ 
  fall, 
  

   or 
  it 
  is 
  emergent 
  (e. 
  g., 
  Scirpus)^ 
  in 
  which 
  case 
  it 
  dies 
  down 
  and 
  

   decays 
  when 
  broken 
  down 
  hj 
  ice 
  and 
  winter 
  floods. 
  The 
  vegetation 
  

   of 
  Flag 
  Lake 
  is 
  rooted, 
  and 
  Kofoid 
  suggests 
  that 
  the 
  richness 
  of 
  the 
  

   lake 
  in 
  plankton 
  is 
  to 
  be 
  attributed 
  to 
  the 
  food 
  materials 
  drawn 
  f 
  rouj 
  

   the 
  soil 
  by 
  these 
  rooted 
  aquatic 
  plants 
  and 
  dissolved 
  in 
  the 
  water 
  l)y 
  

  

  