﻿10 
  JUHLIN-DANNFELT, 
  ON 
  THE 
  DIATOMS 
  OF 
  THE 
  BALTIC 
  SEA. 
  

  

  brown 
  colour 
  to 
  tlie 
  depth 
  of 
  '^j 
  ^ 
  — 
  1 
  feet, 
  if 
  on 
  tlie 
  contrary 
  

   green 
  algae 
  occur 
  in 
  it 
  in 
  greater 
  quantity, 
  only 
  the 
  surface 
  

   is 
  green, 
  and 
  already 
  at 
  the 
  depth 
  of 
  one 
  inch, 
  the 
  mäss 
  gets 
  

   quite 
  black 
  and 
  smells 
  of 
  liydrosulphuric 
  acid. 
  An 
  interesting 
  

   fact 
  is 
  that 
  the 
  diatomaceoias 
  flora 
  of 
  such 
  bays 
  contains 
  quite 
  

   the 
  same 
  species 
  as 
  occur 
  imbedded 
  in 
  the 
  silt 
  from 
  the 
  

   bottom 
  of 
  the 
  peatmosses 
  and 
  in 
  the 
  silty 
  clay 
  from 
  eastern 
  

   Upland 
  which 
  I 
  have 
  examiued, 
  and 
  it 
  is 
  very 
  different 
  in 
  

   its 
  species 
  from 
  that 
  one 
  of 
  the 
  open 
  coast. 
  Here 
  the 
  main 
  

   mäss 
  is 
  constituted 
  by 
  freely 
  floating 
  forms. 
  Especially 
  

   characteristic 
  for 
  these 
  localities 
  are: 
  Campylodiscus 
  Echineis 
  

   K., 
  and 
  Clypeus 
  K., 
  Navicula 
  peregrina 
  K., 
  oblonga 
  K. 
  and 
  ■ 
  

   sculpta 
  Ehb., 
  Nitzschia 
  circumsuta 
  Bail 
  and 
  scalaris 
  Sm., 
  

   Chaetoceros 
  Wighami 
  Btw. 
  ( 
  — 
  only 
  sporangial 
  forms 
  found 
  — 
  ) 
  

   and 
  Melosira 
  Westii 
  Sm. 
  Besides 
  Epithemiae 
  and 
  Amphora 
  

   cymbiforme 
  occur 
  there 
  very 
  commonly, 
  especially 
  ifCharacege 
  

   also 
  grow 
  there, 
  in 
  which 
  case 
  they 
  are 
  fixed 
  on 
  these. 
  

   On 
  the 
  contrary, 
  some 
  species 
  which 
  otherwise 
  occur 
  very 
  

   commonly 
  on 
  the 
  shores 
  of 
  the 
  Baltic, 
  are 
  here 
  very 
  scarce 
  

   or 
  quite 
  missing, 
  such 
  as 
  Ehoicosphenia 
  curvata 
  Geun., 
  Ach- 
  

   nanthes 
  longipes 
  Lgb., 
  brevipes 
  Ag. 
  and 
  subflexilis 
  Ehb., 
  

   Melosira 
  Jurgensii 
  K., 
  M. 
  nummuloides 
  Dillw., 
  and 
  Cocconeis 
  

   Scutellum 
  Ehb. 
  

  

  The 
  nature 
  of 
  the 
  bottom 
  has 
  also 
  a 
  great 
  influence 
  on 
  

   the 
  richness 
  of 
  the 
  Diatomaceous 
  vegetation, 
  so 
  that 
  where 
  

   the 
  bottom 
  consists 
  of 
  stones, 
  these 
  are 
  wholly 
  covered 
  with 
  

   a 
  mucous 
  film 
  of 
  diatoms. 
  A 
  bottom 
  of 
  clay 
  or 
  mud 
  is 
  clad 
  

   with 
  a 
  velvetlike 
  carpet 
  of 
  green 
  algae 
  and 
  Diatoms, 
  and 
  

   when 
  seaweed 
  grows 
  on 
  it, 
  this 
  too 
  is 
  quite 
  covered 
  

   w^ith 
  diatoms. 
  A 
  sandy 
  bottom, 
  on 
  the 
  contrary, 
  is 
  quite 
  

   sterile 
  in 
  respect 
  of 
  diatoms, 
  and 
  in 
  similar 
  localities, 
  — 
  

   for 
  instance 
  the 
  shallow 
  strand 
  of 
  Oland 
  and 
  the 
  southern 
  

   Skåne, 
  — 
  I 
  have 
  generally 
  found 
  no 
  diatoms 
  at 
  all, 
  save 
  on 
  

   the 
  seaweed 
  thrown 
  up 
  by 
  the 
  swell. 
  

  

  On 
  open 
  coasts, 
  where 
  rivers 
  do 
  not 
  make 
  the 
  water 
  

   very 
  fresh, 
  the 
  diatomaceous 
  vegetation 
  of 
  the 
  Baltic 
  is 
  mainly 
  

   composed 
  of 
  brackish 
  species. 
  Among 
  these 
  the 
  most 
  com- 
  

   mon 
  are: 
  Cocconeis 
  Scutellum 
  Ehb., 
  Achnanthes 
  longipes 
  

   Lgb., 
  Mastogloia 
  lanceolata 
  Thw., 
  Gomphonema 
  balticum 
  Cl., 
  

   Synedra 
  pulchella 
  K., 
  and 
  S. 
  affinis 
  K., 
  Brebissonia 
  Boeckii 
  

   Grun., 
  Licmophorse 
  and 
  Melosira 
  Jurgensii 
  K. 
  Utterly 
  com- 
  

  

  