﻿THE 
  ALG.E 
  

  

  227 
  

  

  213. 
  Vaucheria 
  : 
  nutrition. 
  Materials 
  for 
  food-making 
  may 
  

   be 
  absorbed 
  from 
  the 
  moist 
  earth 
  or 
  from 
  the 
  water 
  in 
  which 
  

   this 
  plant 
  grows. 
  The 
  abundant 
  chlorophyll 
  suggests 
  con- 
  

   siderable 
  ability 
  to 
  manufacture 
  its 
  own 
  nutrient 
  substances, 
  

   but 
  this 
  plant 
  is 
  not 
  so 
  

  

  well 
  fitted 
  for 
  securing 
  

   abundant 
  exposure 
  to 
  

   light 
  as 
  is 
  Cladophora. 
  

   It 
  is 
  to 
  be 
  noted 
  that, 
  

   living 
  on 
  the 
  land 
  as 
  

   these 
  plants 
  often 
  do, 
  

   they 
  do 
  not 
  have 
  the 
  

   protection 
  against 
  ex- 
  

   tremes 
  of 
  light 
  and 
  

   temperature 
  

  

  that 
  water 
  gg 
  

  

  algse 
  enjoy. 
  

  

  214. 
  Vaucheria: 
  re- 
  

   production. 
  As 
  sug- 
  

   gested 
  in 
  section 
  212, 
  

   vegetative 
  reproduc- 
  

   tion 
  occurs 
  in 
  this 
  

   plant. 
  Asexual 
  repro- 
  

   duction 
  may 
  be 
  started 
  

   by 
  having 
  the 
  end 
  of 
  

   a 
  branch 
  cut 
  off 
  by 
  a 
  

   cross 
  wall. 
  The 
  part 
  

   that 
  is 
  thus 
  cut 
  off 
  

   proceeds 
  to 
  form 
  a 
  

   large 
  reproductive 
  body 
  

  

  (fig. 
  177, 
  B, 
  (7) 
  ; 
  the 
  wall 
  which 
  surrounds 
  it 
  breaks, 
  and 
  

   after 
  a 
  period 
  of 
  swimming 
  it 
  germinates 
  and 
  forms 
  a 
  new 
  

   plant 
  (fig. 
  177, 
  D). 
  This 
  special 
  reproductive 
  body 
  is 
  called 
  

   a 
  zoospore 
  (animal 
  spore), 
  or 
  swimming 
  spore. 
  The 
  formation 
  

   of 
  zoospores 
  may 
  be 
  induced 
  in 
  the 
  laboratory 
  by 
  keeping 
  

   Vaucheria 
  plants 
  in 
  a 
  dish 
  of 
  shallow 
  water. 
  

  

  FIG. 
  177. 
  Vaucheria 
  

  

  A, 
  branch 
  of 
  a 
  vegetative 
  plant 
  ; 
  B, 
  branch 
  form- 
  

   ing 
  zoospore 
  ; 
  z, 
  young 
  zoospore 
  just 
  emerging 
  

   from 
  the 
  sporangium 
  (s) 
  ; 
  C, 
  a 
  free 
  zoospore 
  ; 
  D, 
  

   zoospore 
  germinating 
  to 
  form 
  a 
  new 
  plant 
  

  

  