﻿THE 
  A.LGM 
  

  

  229 
  

  

  VaucJieria 
  has 
  three 
  methods 
  of 
  reproduction 
  - 
  - 
  vegetative, 
  

   by 
  asexual 
  spores 
  (zoospores), 
  and 
  by 
  sexual 
  spores 
  (oospores). 
  

  

  One 
  plant 
  may 
  use 
  vegetative 
  reproduction 
  at 
  one 
  period 
  

   of 
  growth, 
  asexual 
  spore 
  reproduction 
  at 
  another, 
  and 
  sex 
  

   spore 
  reproduction 
  at 
  another, 
  but 
  two 
  methods 
  are 
  rarely 
  

   used 
  at 
  the 
  same 
  time. 
  

  

  215. 
  Other 
  green 
  algae. 
  Although 
  

   in 
  inland 
  waters 
  green 
  algre 
  are 
  more 
  

   abundant 
  than 
  all 
  others, 
  only 
  two 
  

   other 
  genera 
  will 
  be 
  mentioned 
  in 
  

   this 
  connection. 
  Splicerella, 
  a 
  unicel- 
  

   lular 
  form 
  somewhat 
  like 
  Pleurococcus, 
  

   is 
  frequently 
  found 
  in 
  stagnant 
  water. 
  

   It 
  sometimes 
  grows 
  so 
  luxuriantly 
  in 
  

   barnyard 
  and 
  roadside 
  pools 
  as 
  to 
  

   give 
  the 
  water 
  a 
  bright 
  green 
  appear- 
  

   ance, 
  and 
  its 
  resting 
  spores 
  may 
  im- 
  

   part 
  a 
  dark 
  red 
  color 
  to 
  drying 
  pools 
  

   in 
  which 
  the 
  plants 
  have 
  nourished. 
  

   Chara, 
  or 
  stonewort 
  (fig. 
  179), 
  is 
  a 
  

   complex 
  alga 
  that 
  is 
  found 
  in 
  great 
  

   abundance 
  on 
  the 
  bottoms 
  of 
  shallow 
  

   lakes 
  and 
  streams 
  throughout 
  the 
  

   continent. 
  It 
  lias 
  a 
  heavy 
  coating 
  of 
  

   calcareous 
  material, 
  which, 
  as 
  the 
  

   plant 
  dies, 
  falls 
  to 
  the 
  bottom 
  of 
  the 
  

   pond 
  or 
  stream. 
  Chara 
  grows 
  in 
  such 
  

   luxuriance 
  that 
  its 
  deposits 
  eventually 
  

   form 
  deep 
  layers 
  of 
  this 
  calcareous 
  material, 
  or 
  marl, 
  as 
  it 
  is 
  

   called. 
  Marl 
  has 
  been 
  found 
  of 
  great 
  value 
  as 
  one 
  of 
  the 
  mate- 
  

   rials 
  used 
  in 
  the 
  manufacture 
  of 
  cement, 
  and 
  not 
  a 
  few 
  of 
  the 
  

   lakes 
  in 
  which 
  Chara 
  grows 
  are 
  dredged 
  to 
  secure 
  the 
  marl 
  

   deposits 
  for 
  this 
  important 
  manufacture. 
  

  

  216. 
  Algae 
  and 
  water 
  supply. 
  Many 
  of 
  our 
  large 
  cities 
  have 
  

   found 
  it 
  advisable 
  to 
  adapt 
  or 
  construct 
  reservoirs 
  for 
  water 
  

   supply. 
  These 
  are 
  open 
  pools, 
  lakes, 
  tanks, 
  etc., 
  and 
  they 
  are 
  

  

  FIG. 
  179. 
  The 
  stonewort 
  alga 
  

   (Chara) 
  

  

  A, 
  a 
  slightly 
  magnified 
  piece 
  of 
  

   a 
  plant, 
  showing 
  the 
  general 
  

   appearance 
  ; 
  B, 
  a 
  more 
  highly 
  

   magnified 
  illustration 
  showing 
  

   the 
  oogonium 
  (o) 
  and 
  the 
  an- 
  

   theridium 
  (a), 
  by 
  means 
  of 
  

   which 
  reproduction 
  takes 
  place 
  

  

  