﻿566 
  Setchell: 
  The 
  marixe 
  spermatophytes 
  

  

  intention 
  of 
  this 
  paper 
  to 
  inquire 
  rather 
  into 
  the 
  climatic 
  distri- 
  

   bution 
  of 
  the 
  marine 
  spermatophytes 
  and 
  to 
  compare 
  it 
  with 
  the 
  

   distribution 
  of 
  the 
  marine 
  algae: 
  In 
  attempting 
  to 
  do 
  this, 
  I 
  shall 
  

   try 
  to 
  arrange 
  the 
  different 
  species 
  in 
  the 
  climatic 
  zones 
  already 
  

   outlined 
  by 
  me 
  in 
  previous 
  papers 
  (1915, 
  1917). 
  These 
  climatic 
  

   zones 
  are 
  as 
  follows 
  :— 
  Upper 
  Boreal 
  and 
  Upper 
  Austral 
  of 
  mean 
  

  

  maximum 
  

  

  o 
  _ 
  _o 
  

  

  10° 
  C, 
  Lower 
  Boreal 
  and 
  Lower 
  

   Austral 
  10^-15° 
  C, 
  North 
  Temperate 
  and 
  South 
  Temperate 
  

   i5*'-2o° 
  C, 
  North 
  Subtropical 
  and 
  South 
  Subtropical 
  20°-25'' 
  C, 
  

   and 
  Tropical 
  from 
  25° 
  C. 
  mean 
  maximum 
  up 
  to 
  the 
  limit 
  of 
  29 
  

   or 
  30° 
  C. 
  It 
  seems 
  that 
  the 
  marine 
  spermatophytes 
  ought 
  to 
  

   follow 
  the 
  same 
  temperature 
  laws 
  as 
  the 
  marine 
  thallophytes 
  and 
  

   be 
  found 
  in 
  similar 
  zones 
  and 
  just 
  as 
  closely 
  restricted 
  in 
  their 
  

   distribution. 
  The 
  algae, 
  so 
  far 
  as 
  I 
  am 
  able 
  to 
  determine 
  at 
  

   present, 
  are 
  either 
  restricted 
  to 
  a 
  single 
  zone 
  or, 
  if 
  they 
  extend 
  

   from 
  one 
  zone 
  into 
  others, 
  invade 
  the 
  additional 
  zones" 
  because, 
  

   for 
  some 
  reason 
  or 
  other, 
  they 
  find 
  in 
  the 
  invaded 
  zone, 
  or 
  zones, 
  

   the 
  temperatures 
  characteristic 
  of 
  the 
  zone 
  to 
  which 
  they 
  are 
  

   normal. 
  The 
  reasons 
  for 
  suspecting 
  invasion, 
  even 
  when 
  the 
  

  

  warm 
  

  

  areas, 
  spots 
  and 
  particularly 
  of 
  seasonal 
  minima 
  in 
  warmer 
  zones 
  

   each 
  with 
  its 
  peculiar 
  flora. 
  Since 
  the 
  marine 
  spermatophytes 
  

   inhabit 
  the 
  shallow 
  waters, 
  the 
  criteria 
  of 
  their 
  distribution 
  may 
  

   be 
  considered 
  to 
  be 
  the 
  mean 
  maxima 
  and 
  minima 
  of 
  the 
  surface 
  

   waters 
  5° 
  C. 
  apart, 
  as 
  it 
  is 
  in 
  the 
  case 
  of 
  the 
  great 
  majority 
  of 
  the 
  

   marine 
  algae. 
  

  

  The 
  climatic 
  distribution 
  of 
  the 
  marine 
  spermatophytes 
  has 
  

   been 
  treated 
  of 
  by 
  Ascherson 
  as 
  I 
  have 
  already 
  mentioned. 
  In 
  

   1 
  87 
  1, 
  he 
  published 
  his 
  paper 
  on 
  this 
  subject 
  and 
  discussed 
  and 
  

   represented 
  on 
  maps 
  the 
  distribution 
  of 
  the 
  twenty-two 
  species 
  

   then 
  known 
  to 
  him. 
  In 
  distribution 
  by 
  oceans, 
  Ascherson 
  

   credits 
  one 
  species 
  to 
  the 
  Arctic 
  Ocean, 
  seven 
  to 
  the 
  Atlantic, 
  

   fourteen 
  to 
  the 
  Indian 
  Ocean 
  and 
  thirteen 
  to 
  the 
  Pacific 
  Ocean. 
  

   The 
  Antarctic 
  Ocean 
  has 
  no 
  species 
  credited 
  to 
  it. 
  Ascherson 
  

   discusses 
  the 
  relation 
  of 
  the 
  different 
  species 
  to 
  the 
  climatic 
  zones 
  

   as 
  laid 
  off 
  with 
  reference 
  to 
  the 
  Arctic 
  Circle 
  and 
  the 
  Tropics 
  of 
  

   Cancer 
  and 
  Capricorn. 
  Such 
  a 
  discussion 
  of 
  climatic 
  distribution 
  

   does 
  not 
  lead 
  very 
  far 
  even 
  In 
  connection 
  witli 
  lanH 
  r.1nr.tc 
  cinr^P 
  

  

  