﻿28 
  Gleason: 
  Some 
  applications 
  of 
  the 
  quadrat 
  method 
  

  

  distributed 
  absolutely 
  at 
  random 
  over 
  the 
  association, 
  that 
  is, 
  if 
  

   the 
  association 
  were 
  absolutely 
  uniform 
  throughout^ 
  separated 
  

   quadrats 
  would 
  never 
  be 
  necessary. 
  But 
  plants 
  are 
  not 
  distri- 
  

   buted 
  entirely 
  at 
  random. 
  Each 
  plant-parent 
  gives 
  rise 
  to 
  dis- 
  

   seminules 
  which 
  occupy, 
  roughly 
  speaking, 
  a 
  circle 
  about 
  it, 
  with 
  

   a 
  diameter 
  depending 
  upon 
  the 
  mobility 
  of 
  the 
  disseminules. 
  

   As 
  early 
  as 
  1903 
  the 
  writer 
  (1907, 
  p. 
  159) 
  was 
  able 
  to 
  demonstrate 
  

   these 
  in 
  his 
  field 
  work. 
  As 
  a 
  check, 
  the 
  following 
  data 
  from 
  240 
  

   one-meter 
  quadrats 
  are 
  offered. 
  The 
  2^ 
  species 
  have 
  frequency 
  

   indices 
  ranging 
  from 
  o 
  (i 
  quadrat 
  only) 
  to 
  99, 
  based 
  upon 
  the 
  

   whole 
  series. 
  If 
  any 
  fourth 
  part 
  of 
  the 
  series 
  is 
  taken 
  as 
  a 
  basis, 
  

   composed 
  of 
  60 
  contiguous 
  quadrats, 
  as 
  shown 
  in 
  the 
  last 
  four 
  

   columns 
  of 
  Table 
  I, 
  the 
  average 
  discrepancy 
  between 
  the 
  two 
  

  

  F 
  

  

  series 
  of 
  indices 
  is 
  6.8, 
  or 
  for 
  the 
  15 
  commonest 
  species 
  10.7, 
  

   and 
  the 
  difference 
  may 
  be 
  as 
  high 
  as 
  44 
  for 
  a 
  species 
  which 
  normally 
  

   grows 
  in 
  patches. 
  But 
  if 
  every 
  fourth 
  quadrat 
  is 
  taken 
  as 
  a 
  basis, 
  

   that 
  is, 
  60 
  separated 
  quadrats, 
  as 
  shown 
  in 
  column 
  4 
  of 
  Table 
  I, 
  

   the 
  greatest 
  discrepancy 
  is 
  only 
  9 
  and 
  the 
  average 
  only 
  1.9, 
  or 
  2.7 
  

   for 
  the 
  commonest 
  species. 
  In 
  other 
  words, 
  60 
  quadrats 
  well 
  

   scattered 
  give 
  results 
  practically 
  as 
  reliable 
  as 
  240 
  contiguous 
  ones. 
  

   From 
  a 
  list 
  of 
  the 
  frequency 
  indices, 
  made 
  from 
  quadrats 
  of 
  

   suitable 
  size 
  and 
  number, 
  the 
  species 
  are 
  arranged 
  in 
  order 
  of 
  

   their 
  general 
  distribution 
  in 
  the 
  association, 
  and 
  any 
  number 
  of 
  

   them 
  may 
  be 
  segregated 
  for 
  further 
  study 
  as 
  the 
  most 
  typical 
  or 
  

   commonest. 
  Since 
  the 
  frequency 
  index 
  increases 
  with 
  the 
  size 
  

   of 
  the 
  quadrat, 
  a 
  quadrat 
  of 
  proper 
  size 
  may 
  now 
  be 
  chosen 
  which 
  

   will 
  normally 
  include 
  all 
  the 
  more 
  important 
  species 
  as 
  well 
  as 
  a 
  

   number 
  of 
  the 
  less 
  important 
  ones 
  also. 
  The 
  size 
  of 
  this 
  major 
  

   qiiadrat 
  may 
  be 
  determined 
  in 
  advance 
  and, 
  in 
  field 
  work 
  with 
  

   students, 
  one 
  of 
  them 
  assigned 
  to 
  each 
  student 
  for 
  detailed 
  study 
  

   and 
  description. 
  Although 
  every 
  such 
  major 
  quadrat 
  may 
  not 
  

   actually 
  contain 
  all 
  the 
  important 
  species, 
  the 
  student 
  may 
  be 
  

   assured 
  that 
  it 
  is 
  nevertheless 
  a 
  fair 
  sample 
  of 
  the 
  association 
  as 
  a 
  

   whole. 
  The 
  value 
  of 
  setting 
  a 
  definite 
  area 
  before 
  each 
  student, 
  

   in 
  which 
  he 
  may 
  do 
  his 
  more 
  intensive 
  work, 
  will 
  be 
  at 
  once 
  appar- 
  

   ent 
  to 
  every 
  teacher 
  who 
  has 
  tried 
  to 
  present 
  this 
  phase 
  of 
  ecology 
  

   in 
  the 
  field. 
  The 
  method 
  of 
  determining 
  the 
  major 
  quadrat 
  will 
  

   be 
  discussed 
  below. 
  

  

  