﻿Gleason: 
  Some 
  applications 
  of 
  the 
  quadrat 
  method 
  23 
  

  

  very 
  long 
  period. 
  Minor 
  differences 
  in 
  environment 
  may 
  lead 
  

   to 
  the 
  predominance 
  of 
  certain 
  species 
  in 
  favorable 
  places, 
  to 
  the 
  

   persistence 
  of 
  relics, 
  or 
  to 
  the 
  early 
  appearance 
  of 
  pioneers 
  of 
  other 
  

   associations. 
  Uniformity 
  can 
  not 
  be 
  perfect, 
  although 
  the 
  general 
  

   tendency 
  of 
  vegetation 
  (apart 
  from 
  the 
  effect 
  of 
  disturbing 
  physical 
  

   factors) 
  is 
  always 
  toward 
  uniformity, 
  and 
  it 
  is 
  most 
  nearly 
  attained 
  

   in 
  old 
  (climax) 
  closed 
  associations, 
  where 
  entrance 
  of 
  new 
  species 
  

   is 
  prevented 
  by 
  vegetative 
  control 
  of 
  the 
  environment, 
  or 
  in 
  

   associations 
  of 
  extreme 
  environment, 
  where 
  a 
  small 
  group 
  of 
  

   adjusted 
  species 
  enjoy 
  a 
  monopoly 
  of 
  the 
  area. 
  • 
  . 
  

  

  If 
  the 
  association 
  were 
  absolutely 
  homogeneous, 
  if 
  the 
  plant 
  

   individuals 
  of 
  the 
  different 
  component 
  species 
  were 
  as 
  regularly 
  

   distributed 
  as 
  water 
  and 
  alcohol 
  in 
  a 
  mixture 
  of 
  the 
  two 
  liquids, 
  

   all 
  quadrats 
  of 
  appreciable 
  size 
  would 
  be 
  similar 
  and 
  any 
  quad- 
  

   rat 
  could 
  be 
  chosen 
  to 
  represent 
  the 
  vegetation. 
  Since 
  no 
  

   association 
  is 
  perfectly 
  uniform, 
  any 
  one 
  quadrat 
  may 
  by 
  its 
  

   structure 
  accentuate 
  the 
  variability 
  instead 
  of 
  concealing 
  it. 
  

   The 
  value 
  of 
  a 
  single 
  quadrat 
  also 
  depends 
  on 
  its 
  size 
  and 
  on 
  the 
  

   number 
  of 
  species 
  In 
  the 
  association. 
  In 
  communities 
  of 
  'numerous 
  

   species 
  (75 
  or 
  more), 
  a 
  meter 
  quadrat 
  seldom 
  includes 
  as 
  many 
  as 
  

   fifteen 
  of 
  them 
  and 
  usually 
  contains 
  still 
  fewen 
  In 
  very 
  open 
  

   associations, 
  a 
  meter 
  quadrat 
  frequently 
  Includes 
  but 
  a 
  single 
  

   individual 
  plant. 
  In 
  either 
  case, 
  the 
  error 
  is 
  reduced 
  by 
  increasing 
  

   the 
  size 
  of 
  the 
  quadrat, 
  but 
  this 
  simultaneously 
  increases 
  the 
  labor 
  

   of 
  charting 
  and 
  decreases 
  the 
  value 
  of 
  a 
  photograph. 
  

  

  ■The 
  single 
  quadrat 
  of 
  small 
  size, 
  one 
  to 
  two 
  meters 
  square, 
  is 
  

   therefore 
  essential 
  for 
  graphic 
  illustration, 
  either 
  by 
  photograph 
  or 
  

   map, 
  and 
  is 
  undoubtedly 
  of 
  value 
  also 
  for 
  experimental 
  work, 
  

   but 
  it 
  fails 
  to 
  give 
  a 
  fair 
  representation 
  of 
  the 
  whole 
  association, 
  

   and 
  is 
  of 
  less 
  value 
  as 
  a 
  basis 
  for 
  written 
  description 
  or 
  as 
  a 
  unit 
  

   for 
  intensive 
  study 
  in 
  field 
  work. 
  To 
  be 
  sure, 
  a 
  suitable 
  quadrat 
  

   may 
  be 
  chosen, 
  but 
  the 
  quadrat 
  method 
  itself, 
  as 
  ordinarily 
  used, 
  

   offers 
  no 
  aid 
  in 
  the 
  selection 
  of 
  this 
  typical 
  area, 
  so 
  the 
  actual 
  

   choice 
  invariably 
  represents 
  the 
  observer's 
  idea 
  rather 
  than 
  the 
  

   impersonal 
  facts. 
  

  

  IT 
  

  

  The 
  chief 
  value 
  of 
  the 
  quadrat 
  method 
  lies 
  in 
  the 
  results 
  ob- 
  

   tained 
  from 
  the 
  study 
  of 
  many 
  quadrats, 
  chosen 
  at 
  random 
  to 
  

   avoid 
  the 
  personal 
  element, 
  scattered 
  over 
  an 
  area 
  wide 
  enough 
  

  

  