﻿570 
  Setchell: 
  The 
  marine 
  spermatophytes 
  

  

  1 
  

  

  ditions 
  of 
  terrestrial 
  spermatophytes 
  in 
  that, 
  at 
  periods 
  of 
  low 
  

   water, 
  they 
  have 
  their 
  roots 
  in 
  soil 
  (or 
  sand) 
  of 
  one 
  temperature 
  

   and 
  their 
  leaves 
  in 
  air 
  of 
  another. 
  The 
  majority 
  of 
  the 
  marine 
  

   spermatophytes 
  live 
  under 
  a 
  greater 
  uniformity 
  of 
  temperature 
  

   conditions 
  than 
  do 
  the 
  terrestrial 
  spermatophytes. 
  

  

  2. 
  The 
  marine 
  spermatophytes 
  live 
  under 
  conditions 
  very 
  

   similar 
  to 
  those 
  experienced 
  by 
  the 
  marine 
  algae 
  and 
  show 
  the 
  

   same 
  temperature-zone 
  relations 
  as 
  the 
  marine 
  algae. 
  

  

  3- 
  The 
  great 
  majority 
  of 
  the 
  species 
  of 
  the 
  marine 
  spermato- 
  

   phytes 
  are 
  confined 
  strictly 
  to 
  one 
  temperature 
  zone 
  of 
  5° 
  C. 
  

   amplitude 
  of 
  the 
  monthly 
  mean 
  maximum 
  of 
  the 
  surface 
  waters. 
  

  

  from 
  

  

  may 
  

  

  4. 
  There 
  are 
  certain 
  species 
  which 
  extend 
  over 
  two 
  zones 
  of 
  

   temperature. 
  It 
  seems 
  possible 
  in 
  these 
  cases, 
  as 
  it 
  has 
  also 
  

   seemed 
  possible 
  in 
  the 
  cases 
  of 
  certain 
  marine 
  algae, 
  to 
  regard 
  

   these 
  marine 
  spermatophytes 
  as 
  normal 
  to 
  one 
  zone 
  whence 
  they 
  

   invade 
  the 
  other 
  because 
  they 
  find 
  in 
  certain 
  localities 
  of 
  the 
  in- 
  

   vaded 
  zone 
  their 
  proper 
  temperature, 
  both 
  as 
  to 
  intensity 
  and 
  

   duration. 
  The 
  invasions 
  of 
  the 
  marine 
  spermatophytes, 
  like 
  

   those 
  of 
  the 
  marine 
  algae, 
  proceed 
  in 
  tsv-o 
  directions 
  in 
  the 
  cases 
  

   of 
  the 
  two-zoned 
  species, 
  viz., 
  from 
  a 
  warmer 
  into 
  a 
  colder 
  zone 
  

   because 
  of 
  the 
  existence 
  of 
  warmer 
  spots 
  among 
  the 
  colder 
  areas 
  

   normal 
  to 
  the 
  zone, 
  or 
  from 
  a 
  colder 
  into 
  a 
  warmer 
  zone 
  because 
  

  

  of 
  a 
  seasonal 
  lowering 
  of 
  the 
  temperature 
  of 
  the 
  warmer 
  zone 
  or 
  

   portions 
  of 
  it. 
  

  

  {ij.>5i-There 
  are 
  a 
  few 
  species 
  which 
  are 
  credited 
  to 
  more 
  than 
  

   tWo 
  temperature 
  zones 
  and 
  such 
  are 
  also 
  found 
  among 
  the 
  marine 
  

   algae." 
  f 
  It 
  may 
  be 
  that 
  these 
  species 
  being 
  normal 
  to 
  one 
  tem- 
  

  

  -I 
  

  

  peratufe>'zt>ne, 
  may 
  invade 
  not 
  only 
  one 
  zone, 
  but 
  two 
  or 
  more 
  

   additional 
  zones 
  because 
  of 
  the 
  existence 
  of 
  localities 
  or 
  seasons 
  

   suitable 
  fitlemperature. 
  This 
  movement 
  may 
  be 
  in 
  only 
  one 
  

   direfctii^h 
  ftioiil 
  J<ihe 
  normal 
  zone, 
  as 
  in 
  the 
  case 
  of 
  HalopUla 
  oralis, 
  

   or 
  it 
  may 
  be 
  in 
  two 
  directions 
  from 
  the 
  normal 
  zone, 
  as 
  seems 
  to 
  

   ^bte^thfcVMfcf'WrthffZfX^/era 
  marina. 
  

  

  onti6.r^FmallyT«te^htH^On 
  may 
  be 
  called 
  to 
  the 
  difficulties 
  attending 
  

   thV 
  ^ttiByASf 
  >the/icW«i^ibution 
  of 
  a 
  species 
  caused 
  by 
  the 
  incom- 
  

   pletenfe8d'<3f"OtIt'fk«iWltdge 
  of 
  its 
  homoeeneitv 
  or 
  the 
  l^rk 
  nf 
  it 
  

  

  bf 
  

  

  