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  INTRODUCTION 
  TO 
  BOTANY 
  

  

  intended 
  to 
  hold 
  water 
  enough 
  so 
  that 
  there 
  will 
  be 
  a 
  suf- 
  

   ficient 
  supply 
  in 
  times 
  of 
  scarcity. 
  Such 
  reservoirs 
  have 
  

   proved 
  so 
  admirable 
  as 
  growing 
  places 
  for 
  algae 
  that 
  these 
  

   plants 
  often 
  become 
  a 
  nuisance. 
  Their 
  presence 
  in 
  water 
  for 
  

   domestic 
  use 
  is 
  not 
  attractive, 
  and, 
  besides, 
  they 
  may 
  stop 
  

   up 
  the 
  water 
  pipes. 
  But 
  far 
  more 
  serious 
  than 
  these 
  objec- 
  

   tions 
  is 
  the 
  actual 
  pollution 
  of 
  the 
  water 
  because 
  of 
  their 
  

   presence. 
  When 
  they 
  die 
  they 
  become 
  the 
  food 
  for 
  decay- 
  

   producing 
  organisms, 
  and 
  often 
  positively 
  injurious 
  substances 
  

   are 
  generated. 
  It 
  has 
  been 
  found 
  that 
  by 
  towing 
  about 
  in 
  

   such 
  reservoirs 
  a 
  quantity 
  of 
  copper 
  sulphate 
  inclosed 
  in 
  coarse 
  

   sacking, 
  minute 
  quantities 
  of 
  the 
  salt 
  become 
  dissolved 
  and 
  

   the 
  algre 
  are 
  thus 
  killed. 
  The 
  solution 
  is 
  not 
  strong 
  enough 
  

   to 
  render 
  the 
  water 
  unwholesome 
  for 
  use. 
  This 
  treatment 
  

   has 
  been 
  an 
  important 
  factor 
  in 
  improving 
  the 
  water 
  in 
  many 
  

   A 
  merican 
  cities. 
  1 
  

  

  217. 
  The 
  brown 
  algae. 
  The 
  remaining 
  groups 
  of 
  algse, 
  

   though 
  almost 
  exclusively 
  salt-water 
  plants, 
  have 
  such 
  strik- 
  

   ing 
  characteristics 
  that 
  brief 
  mention 
  of 
  them 
  must 
  be 
  made, 
  

   and 
  pupils 
  who 
  live 
  near 
  the 
  seacoast 
  will 
  be 
  interested 
  in 
  

   extending 
  this 
  study. 
  The 
  brown 
  alga?, 
  or 
  brown 
  seaweeds, 
  

   are 
  found 
  along 
  the 
  shores 
  of 
  all 
  the 
  oceans. 
  They 
  grow 
  

   attached, 
  by 
  menus 
  of 
  strong 
  holdfasts, 
  to 
  rocks, 
  piling, 
  or 
  

   any 
  relatively 
  fixed 
  support 
  that 
  is 
  available. 
  

  

  From 
  high-tide 
  mark 
  to 
  a 
  little 
  below 
  low-water 
  mark 
  cer- 
  

   tain 
  brown 
  algre, 
  known 
  as 
  rockweeds 
  (/'mm- 
  and 
  Ascophyllum 
  ) 
  

   ( 
  Tig. 
  180), 
  often 
  form 
  dense 
  coatings 
  upon 
  rocks. 
  At 
  low 
  tide 
  

   these 
  rockweeds 
  hang 
  loosely 
  over 
  the 
  exposed 
  rocks, 
  and 
  

   exhibit 
  the 
  characteristic 
  dark 
  olive-green 
  color. 
  

  

  The 
  brown 
  algre 
  sometimes 
  become 
  detached 
  and 
  are 
  car- 
  

   ried 
  hundreds 
  or 
  even 
  thousands 
  of 
  miles 
  from 
  their 
  original 
  

  

  1 
  See 
  "A 
  Method 
  of 
  Destroying 
  or 
  Preventing 
  the 
  Growth 
  of 
  Algse 
  

   and 
  Certain 
  Pathogenic 
  Bacteria 
  in 
  Water 
  Supplies" 
  and 
  "Copper 
  as 
  

   an 
  Algieide 
  and 
  Disinfectant 
  in 
  Water 
  Supplies." 
  Hnlletin 
  64 
  (1904) 
  and 
  

   Hull, 
  /in 
  ;v; 
  (1905), 
  respectively, 
  Bureau 
  of 
  1'lant 
  Industry, 
  U.S. 
  Dept. 
  Agr.; 
  

   also 
  Whipple. 
  Microscopy 
  of 
  Drinking 
  Water, 
  chap, 
  xii, 
  John 
  Wiley 
  & 
  Sons, 
  

   New 
  York, 
  1900. 
  

  

  