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  Nichols: 
  The 
  vegetation 
  of 
  Connecticut 
  545 
  

  

  rate 
  more 
  rapid 
  than 
  that 
  at 
  which 
  the 
  marsh 
  surface 
  is 
  being 
  

   built 
  up 
  would 
  lead 
  to 
  an 
  order 
  of 
  succession 
  more 
  or 
  less 
  com- 
  

   pletely 
  the 
  reverse 
  of 
  the 
  apparent 
  order 
  earlier 
  outlined, 
  i.e,, 
  the 
  

   succession 
  of 
  plant 
  associations 
  would 
  be 
  retrogressive; 
  and, 
  fur- 
  

   ther, 
  that 
  a 
  rate 
  of 
  subsidence 
  exactly 
  counter-balancing 
  that 
  at 
  

   which 
  the 
  marsh 
  surface 
  is 
  being 
  built 
  up 
  would 
  favor 
  a 
  complete 
  

   absence 
  of 
  change 
  in 
  the 
  character 
  of 
  the 
  surface 
  vegetation, 
  i.e., 
  

  

  ¥ 
  _ 
  

  

  there 
  would 
  tend 
  to 
  be 
  no 
  succession 
  whatever. 
  Only 
  where 
  the 
  

   rate 
  of 
  upbuilding 
  exceeds 
  that 
  of 
  submergence 
  could 
  the 
  actual 
  

  

  ^ 
  

  

  succession 
  of 
  plant 
  associations 
  be 
  expected 
  to 
  coincide 
  with 
  the 
  

   apparent 
  succession, 
  i.e., 
  only 
  under 
  these 
  conditions 
  could 
  a 
  

   progressive 
  succession 
  take 
  place; 
  and 
  whether 
  any 
  such 
  correla- 
  

   tion 
  ever 
  actually 
  exists 
  remains 
  to 
  be 
  demonstrated. 
  The 
  coastal 
  

   subsidence 
  explanation 
  for 
  the 
  invasion 
  of 
  fresh 
  swamps 
  by 
  salt 
  

   water, 
  and 
  similar 
  phenomena, 
  is 
  scouted 
  by 
  D. 
  W. 
  Johnson 
  

   C13), 
  who 
  would 
  account 
  for 
  the 
  observed 
  facts 
  in 
  other 
  ways; 
  

   but 
  Johnson's 
  arguments 
  are 
  not 
  wholly 
  convincing. 
  

  

  Origin 
  of 
  salt 
  marsh 
  depressions 
  j 
  or 
  ''^aw^."— 
  Mention 
  has 
  been 
  

  

  r 
  ^ 
  

  

  made 
  in 
  an 
  earlier 
  paragraph 
  (p, 
  531) 
  of 
  the 
  occurrence, 
  particularly 
  

   in 
  the 
  meadows 
  of 
  the 
  upper 
  littoral, 
  of 
  poorly 
  drained 
  depressions, 
  

   which 
  differ 
  greatly 
  in 
  the 
  character 
  of 
  their 
  vegetation 
  from 
  ad- 
  

   joining 
  portions 
  of 
  the 
  marsh 
  (Figs. 
  -7, 
  lo). 
  The 
  origin 
  of 
  these 
  

  

  r 
  

  

  depressions, 
  which 
  range 
  in 
  depth 
  from 
  a 
  fraction 
  of 
  an 
  inch 
  to 
  

   well 
  over 
  a 
  foot, 
  has 
  been 
  variously 
  accounted 
  for. 
  Harshberger 
  

   C16) 
  attributes 
  them 
  to 
  masses 
  of 
  tidal 
  trash 
  (consisting 
  commonly 
  

   of 
  dead 
  stems 
  and 
  leaves 
  of 
  eel 
  grass 
  and 
  salt 
  marsh 
  grass, 
  but 
  in 
  

   many 
  cases^see 
  Johnson 
  and 
  York, 
  '15 
  — 
  made 
  up 
  largely 
  of 
  loose- 
  

   floating 
  Ulva 
  and 
  Enteromorpha) 
  which 
  in 
  times 
  of 
  exceptionally 
  

   high 
  water 
  are 
  swept 
  in 
  over 
  the 
  surface 
  of 
  the 
  meadow 
  by 
  tidal 
  

   currents 
  and, 
  settling 
  down 
  there 
  (particularly 
  in 
  places 
  where 
  the 
  

   vegetation 
  already 
  has 
  become 
  matted 
  and 
  twisted 
  by 
  winds 
  and 
  

   waves, 
  as 
  shown 
  in 
  Fig. 
  6), 
  smother 
  out 
  the 
  existing 
  plant 
  cover. 
  

   Subsequently, 
  he 
  maintains, 
  rapid 
  decay 
  sets 
  in, 
  affecting 
  not 
  only 
  

   the 
  aerial 
  plant 
  organs 
  but 
  the 
  underground 
  parts 
  as 
  well, 
  and 
  

   eventually 
  a 
  depression 
  of 
  some 
  depth 
  may 
  thus 
  arise. 
  This 
  ex- 
  

   planation, 
  which 
  is 
  also 
  suggested 
  by 
  Johnson 
  and 
  York 
  ('15, 
  

   pp. 
  21, 
  22, 
  47, 
  etc.), 
  accounts 
  in 
  a 
  wholly 
  satisfactory 
  manner 
  for 
  

   the 
  origin 
  of 
  the 
  essentially 
  flat 
  barren 
  spots, 
  which 
  are 
  of 
  frequent 
  

  

  