﻿568 
  Setchell: 
  The 
  marine 
  spermatophytes 
  

  

  nized. 
  Of 
  these 
  eighteen 
  are 
  confined 
  to 
  the 
  tropical 
  zone 
  of 
  

  

  marine 
  

  

  maximum 
  

  

  four 
  to 
  subtropical 
  zones 
  in 
  that 
  they 
  inhabit 
  marine 
  waters 
  of 
  a 
  

   mean 
  maximum 
  of 
  20° 
  to 
  25° 
  C, 
  while 
  four 
  are 
  inhabitants 
  of 
  

   strictly 
  temperate 
  zones, 
  whose 
  mean 
  maxima 
  range 
  from 
  15° 
  

   to 
  20° 
  C. 
  These 
  twenty-six 
  species 
  certainly 
  seem 
  typically 
  

   stenothermal, 
  being 
  limited 
  to 
  zones 
  of 
  amplitudes 
  of 
  5° 
  C, 
  for 
  

   the 
  hottest 
  month 
  of 
  the 
  year, 
  as 
  to 
  their 
  persistence. 
  The 
  

   remaining 
  eight 
  species 
  are 
  reported 
  as 
  extending 
  over 
  two 
  or 
  

   more 
  zones 
  (of 
  5° 
  C. 
  mean 
  maxima 
  each) 
  and 
  consequently, 
  there- 
  

   fore, 
  more 
  or 
  less 
  eury 
  thermal. 
  Of 
  these 
  one 
  species 
  is 
  credited 
  

   with 
  occupying 
  both 
  tropical 
  and 
  subtropical 
  zones, 
  five 
  species 
  

   with 
  occupying 
  both 
  subtropical 
  and 
  temperate 
  zones, 
  one 
  species 
  

   as 
  occupying 
  tropical, 
  subtropical 
  and 
  temperate 
  zones, 
  while 
  one 
  

   Species 
  is 
  credited 
  with 
  occupying 
  both 
  boreal 
  zones 
  as 
  well 
  as 
  

   temperate, 
  subtropical 
  and 
  tropical 
  zones 
  or 
  five 
  zones 
  in 
  all. 
  

   The 
  last 
  species 
  is, 
  if 
  properly 
  referred 
  to 
  all 
  the 
  zones 
  it 
  is 
  said 
  to 
  

   inhabit, 
  a 
  most 
  typically 
  eurythermal 
  species. 
  It 
  seems 
  best, 
  

   however, 
  to 
  inquire 
  into 
  the 
  particulars 
  of 
  the 
  distribution 
  of 
  these 
  

   seemingly 
  eurythermal 
  species 
  and 
  to 
  attempt 
  to 
  determine 
  so 
  

  

  I 
  

  

  them 
  of 
  such 
  extensive 
  ranges. 
  

  

  i 
  

  

  The 
  cases 
  of 
  species 
  credited 
  with 
  inhabiting 
  two 
  zones 
  do 
  not 
  

   seem 
  very 
  difficult 
  of 
  explanation 
  on 
  a 
  strictly 
  stenothermal 
  basis. 
  

   In 
  other 
  words, 
  such 
  species 
  may 
  be 
  found 
  to 
  belong 
  strictly 
  to 
  

   one 
  or 
  other 
  of 
  the 
  zones 
  they 
  inhabit 
  and 
  invade 
  the 
  second 
  zone 
  

   only 
  because 
  they 
  find 
  at 
  certain 
  places, 
  or 
  at 
  certain 
  seasons, 
  the 
  

  

  same 
  

  

  lo 
  examine 
  into 
  difficult 
  cases, 
  we 
  may 
  select 
  Zostera 
  caprkorni 
  

   Ascherson, 
  which 
  is 
  said 
  to 
  extend 
  from 
  Cape 
  York 
  in 
  tropical 
  

   eastern 
  Australia 
  to 
  Port 
  Jackson 
  in 
  subtropical 
  eastern 
  Australia. 
  

   It 
  will 
  needs 
  be 
  uncertain 
  until 
  this 
  species 
  is 
  better 
  known, 
  as 
  to 
  

   just 
  which 
  zone 
  is 
  to 
  be 
  considered 
  normal 
  for 
  this 
  species, 
  but 
  

   the 
  distribution 
  indicates 
  that 
  the 
  South 
  Subtropical 
  Zone 
  is 
  the 
  

   normal 
  zone 
  since 
  Z. 
  capricorni 
  extends 
  only 
  partially 
  into 
  the 
  

   Tropical 
  Zone. 
  The 
  invasion 
  of 
  the 
  Tropical 
  Zone, 
  in 
  this 
  case, 
  

   may 
  be 
  seasonal 
  and 
  this 
  supposition 
  is 
  strengthened 
  by 
  obser%-ing 
  

  

  