﻿148 
  On 
  the 
  new 
  Flora 
  of 
  Krakatao. 
  

  

  Lyngbya 
  Verbeekiana, 
  thickness 
  without 
  sheaths 
  from 
  1"9 
  

   to 
  3*4 
  /it, 
  with 
  sheaths 
  from 
  5 
  to 
  6*8 
  /x. 
  

  

  Lyngbya 
  minutissima 
  , 
  maximum 
  thickness, 
  without 
  sheaths 
  

   1*03 
  /a, 
  with 
  sheaths 
  1*38 
  /j,. 
  

  

  Lyngbya 
  intermedia, 
  thickness 
  without 
  sheaths 
  from 
  1*73 
  

   to 
  3*45 
  fi, 
  with 
  sheaths 
  from 
  1*73 
  to 
  3*45 
  //.*. 
  

  

  By 
  far 
  the 
  most 
  common 
  of 
  these 
  species 
  is 
  Lyngbya 
  Ver- 
  

   beekiana 
  ; 
  next 
  comes 
  Lyngbya 
  minutissima. 
  These 
  two 
  

   Algae 
  very 
  frequently 
  emerge 
  from 
  their 
  sheaths. 
  

  

  Thanks 
  to 
  these 
  six 
  species 
  of 
  Algae 
  and 
  to 
  their 
  empty 
  

   sheaths, 
  especially 
  of 
  the 
  two 
  Lyngbyce 
  I 
  have 
  just 
  mentioned, 
  

   the 
  arid 
  soil 
  of 
  Krakatao 
  is 
  covered 
  with 
  a 
  thin 
  gelatinous 
  and 
  

   hygroscopic 
  layer. 
  There 
  is 
  no 
  doubt 
  in 
  my 
  mind 
  that 
  the 
  

   presence 
  of 
  this 
  layer 
  alone 
  enables 
  the 
  spores 
  of 
  the 
  ferns 
  and 
  

   of 
  mosses 
  to 
  germinate. 
  On 
  one 
  of 
  the 
  samples 
  of 
  the 
  soil 
  of 
  

   Krakatao 
  I 
  found 
  a 
  spore 
  of 
  Pteris 
  longifolia 
  with 
  a 
  germi- 
  

   native 
  filament 
  of 
  three 
  cells 
  imprisoned 
  in 
  a 
  network 
  of 
  

   sheaths 
  of 
  Lyngbya 
  Verbeekiana. 
  

  

  The 
  Algae 
  prepare 
  the 
  earth 
  for 
  the 
  Ferns 
  in 
  some 
  such 
  

   manner 
  as 
  the 
  latter 
  do 
  in 
  their 
  turn 
  for 
  the 
  Phanerogams. 
  

  

  Let 
  us 
  now 
  suppose 
  for 
  an 
  instant 
  that 
  Krakatao, 
  instead 
  

   of 
  being 
  only 
  a 
  score 
  of 
  miles 
  from 
  Java 
  and 
  from 
  Sumatra, 
  

   was 
  isolated 
  in 
  the 
  sea 
  at 
  a 
  very 
  great 
  distance 
  from 
  all 
  

   plant-bearing 
  land. 
  What 
  would 
  take 
  place 
  ? 
  The 
  belt 
  of 
  

   phanerogams 
  installed 
  on 
  the 
  littoral 
  of 
  the 
  island 
  would 
  

   climb 
  the 
  mountain 
  up 
  to 
  a 
  certain 
  height, 
  driving 
  back 
  the 
  

   ferns. 
  This 
  progress 
  would 
  only 
  be 
  arrested 
  at 
  an 
  altitude 
  

   which 
  no 
  longer 
  suited 
  the 
  elements 
  of 
  the 
  littoral 
  flora. 
  

   Considering 
  the 
  isolation 
  of 
  the 
  island, 
  the 
  seeds 
  of 
  other 
  

   phanerogams, 
  fitted 
  for 
  existence 
  at 
  greater 
  altitudes, 
  would 
  

   never 
  or 
  hardly 
  ever 
  arrive 
  at 
  this 
  station 
  lost 
  in 
  the 
  ocean. 
  

   Consequently 
  the 
  ferns 
  would 
  retain 
  their 
  predominance 
  for 
  

   all 
  time 
  in 
  the 
  higher 
  regions 
  of 
  the 
  island, 
  in 
  company 
  per- 
  

   haps 
  with 
  some 
  Lycopods, 
  and 
  the 
  phanerogams 
  would 
  remain 
  

   restricted 
  to 
  the 
  lower 
  regions 
  and 
  to 
  the 
  shore. 
  

  

  What 
  we 
  have 
  just 
  supposed 
  for 
  Krakatao 
  is 
  realized 
  in 
  

   the 
  cases 
  of 
  Juan 
  Fernandez 
  and 
  Ascension. 
  

  

  Juan 
  Fernandez, 
  a 
  small 
  volcanic 
  island, 
  is 
  situated 
  400 
  

   miles 
  from 
  the 
  coast 
  of 
  Chili. 
  Mr. 
  Moseley 
  says 
  of 
  its 
  flora 
  : 
  — 
  

   " 
  There 
  are 
  upwards 
  of 
  twenty-four 
  species 
  of 
  ferns 
  growing 
  

   in 
  this 
  small 
  island, 
  and 
  in 
  any 
  general 
  view 
  the 
  ferns 
  form 
  

   a 
  large 
  proportion 
  of 
  the 
  main 
  mass 
  of 
  vegetation." 
  

  

  Ascension, 
  an 
  entirely 
  volcanic 
  island 
  of 
  about 
  the 
  same 
  

   height 
  as 
  Krakatao, 
  has 
  a 
  soil 
  which 
  has 
  been 
  described 
  

   thus 
  : 
  — 
  " 
  St. 
  Helena 
  has 
  been 
  called 
  a 
  barren 
  rock, 
  but 
  it 
  is 
  a 
  

   * 
  So 
  in 
  the 
  original. 
  — 
  Eds. 
  ' 
  Annals.' 
  

  

  