﻿572 
  Setchell: 
  The 
  marine 
  spermatophytes 
  

  

  Zone 
  (Florida 
  and 
  the 
  Riu-Kiu 
  Islands). 
  This 
  is 
  certainly 
  a 
  

   perennial 
  species 
  and 
  one 
  capable 
  of 
  wide 
  dispersal. 
  It 
  seems 
  to 
  

  

  m 
  

  

  are 
  buried 
  and 
  floats 
  long 
  distances 
  because 
  of 
  the 
  gases 
  contained 
  

   within 
  the 
  numerous 
  air-passages 
  within 
  its 
  leaves. 
  There 
  is 
  

   good 
  reason, 
  also, 
  for 
  suspecting 
  that 
  two, 
  or 
  even 
  three, 
  distinct 
  

   genetic 
  entitles 
  are 
  included 
  under 
  this 
  specific 
  name, 
  if 
  not 
  at 
  

   least 
  two 
  distinct 
  taxonomic 
  species. 
  The 
  typical 
  Zostera 
  marina 
  

   is 
  generally 
  considered 
  to 
  be 
  the 
  flat- 
  and 
  broad-leaved 
  form 
  while 
  

   a 
  variety 
  with 
  somewhat 
  shorter, 
  narrower 
  and 
  thicker 
  leaves 
  is 
  

   called 
  var. 
  angustifolia 
  Hornemann. 
  There 
  seems 
  also 
  to 
  be 
  a 
  

   form 
  intermediate 
  between 
  the 
  two 
  and 
  this 
  corresponds, 
  in 
  part 
  

   at 
  least, 
  to 
  f 
  . 
  stenophylla 
  Aschers. 
  & 
  Graebner. 
  The 
  species 
  and 
  var. 
  

   angustifolia 
  often 
  occur 
  together, 
  but 
  apparently 
  always 
  separated 
  

   according 
  to 
  substratum 
  and 
  somewhat 
  possibly 
  according 
  to 
  

   depth, 
  the 
  variety 
  in 
  a 
  belt 
  above 
  that 
  occupied 
  by 
  the 
  species 
  and 
  

   restricted 
  to 
  a 
  firmer 
  substratum. 
  Ostenfeld, 
  in 
  1908, 
  made 
  a 
  

   series 
  of 
  studies 
  and 
  careful 
  measurements 
  of 
  these 
  various 
  forms 
  

   and 
  came 
  to 
  the 
  conclusion 
  that 
  the 
  differences 
  were 
  the 
  results 
  

   of 
  more 
  favorable 
  vs. 
  less 
  favorable 
  environment- 
  I 
  am 
  inclined 
  

   to 
  suspect, 
  nevertheless, 
  that 
  there 
  are 
  at 
  least 
  two 
  genetically 
  

  

  r 
  

  

  distinct 
  varieties, 
  or 
  even 
  species, 
  which 
  overlap 
  in 
  their 
  distri- 
  

   bution, 
  the 
  narrow-leaved 
  variety 
  preferring 
  shallower 
  water 
  

   and 
  firmer 
  substratum 
  than 
  the 
  broader-leaved 
  form 
  (or 
  forms) 
  

   and 
  being 
  able 
  to 
  extend 
  farther 
  into 
  the 
  areas 
  of 
  colder 
  waters 
  than 
  

   the 
  broader-leaved 
  forms, 
  Ver>' 
  little 
  seems 
  to 
  have 
  been 
  done 
  as 
  

   yet 
  as 
  to 
  the 
  collection 
  and 
  study 
  of 
  the 
  flowers 
  and 
  fruits, 
  and 
  

   especially 
  of 
  ripe 
  seeds, 
  at 
  various 
  localities 
  in 
  the 
  range 
  and 
  this 
  

   leaves 
  much 
  to 
  be 
  desired 
  especially 
  as 
  regards 
  seasonal 
  data. 
  

  

  On 
  the 
  coasts 
  of 
  Europe, 
  Zostera 
  marina, 
  in 
  one 
  form 
  or 
  another, 
  

   has 
  been 
  given 
  a 
  range 
  from 
  Iceland 
  and 
  the 
  extreme 
  north 
  of 
  

   Europe 
  to 
  and 
  including 
  the 
  Mediterranean 
  Sea, 
  but, 
  as 
  near 
  as 
  I 
  

   am 
  able 
  to 
  determine, 
  the 
  extreme 
  northern 
  locality, 
  viz., 
  WTiite 
  

   Island 
  in 
  the 
  Kara 
  Sea 
  is 
  based 
  on 
  the 
  report 
  of 
  a 
  non-botanist 
  

   (cf. 
  Ascherson, 
  1906, 
  p. 
  ^02). 
  It 
  seems 
  to 
  stop, 
  so 
  far 
  as 
  general 
  

   and 
  continuous 
  distribution 
  is 
  concerned, 
  at 
  Tromsoe, 
  Norway, 
  

   or 
  somewhat 
  below, 
  but 
  does 
  occur 
  in 
  the 
  Varanger 
  Fiord 
  and 
  in 
  

   Porsanger 
  Fiord 
  and 
  in 
  the 
  White 
  Sea 
  on 
  the 
  northern 
  coast 
  of 
  

  

  