﻿220 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  The 
  bluish-green 
  balls 
  (fig. 
  172, 
  A) 
  of 
  Nostoc 
  plants 
  are 
  

   found 
  upon 
  damp 
  soil 
  or 
  lloating 
  14)011 
  stagnant 
  water. 
  I'nder 
  

   magnification 
  1 
  the 
  Nostoc 
  ball 
  is 
  seen 
  to 
  be 
  composed 
  of 
  

  

  granular 
  jelly, 
  inter- 
  

   woven 
  by 
  many 
  chains 
  

   of 
  cells, 
  each 
  of 
  which 
  

   is 
  a 
  Nostoc 
  plant 
  (lig. 
  

   172,7;). 
  These 
  chains 
  

   often 
  divide 
  into 
  two 
  

   or 
  more 
  shorter 
  chains, 
  

   breaking 
  where 
  then- 
  

   are 
  large, 
  dead 
  cells 
  

   ( 
  //,7<r<y/.v7x 
  ), 
  and 
  each 
  

   chain 
  proceeds 
  to 
  live 
  

   as 
  a 
  new 
  plant. 
  Nos- 
  

   toc 
  may 
  absorb 
  the 
  

   materials 
  needed 
  for 
  

   ph< 
  >tosy 
  n 
  thesis 
  directly 
  

   through 
  the 
  cell 
  walls, 
  

   or 
  it 
  may 
  perhaps 
  ab- 
  

   sorb 
  organized 
  foods 
  as 
  

   do 
  the 
  bacteria, 
  since 
  

   much 
  food 
  of 
  this 
  kind 
  

   is 
  present 
  in 
  the 
  water 
  

   in 
  which 
  the 
  plants 
  live. 
  

   In 
  times 
  of 
  drought 
  the 
  

   jelly 
  balls 
  dry 
  slowly 
  

   and 
  may 
  become 
  dry 
  

   ei 
  1 
  1 
  nigh 
  to 
  crumble 
  eas- 
  

   ily, 
  but 
  when 
  a 
  favora- 
  

   ble 
  amount 
  of 
  moisture 
  

   returns, 
  the 
  plants 
  within 
  the 
  ball 
  may 
  proceed 
  to 
  grow. 
  

  

  B 
  

  

  FIG. 
  17-2. 
  Nostoc 
  

  

  At 
  the 
  left 
  (.1) 
  are 
  several 
  of 
  the. 
  NostOC 
  halls, 
  

   \vhieli 
  appeal 
  1 
  as 
  ^listeiiin.i;, 
  rounded 
  masses 
  (nat- 
  

   ural 
  si/.e). 
  At 
  tile 
  right 
  (B), 
  inclosed 
  in 
  udatiunus 
  

   material, 
  are 
  a 
  few 
  chains 
  of 
  \nxtn,- 
  plants 
  \\hich 
  

   have 
  been 
  taken 
  from 
  one 
  of 
  the 
  halls 
  and 
  

   mai, 
  r 
  nitied. 
  In 
  tlie 
  chains 
  se\ 
  cral 
  of 
  the 
  e 
  

   heterocvsts 
  mav 
  he 
  seen 
  

  

  1 
  When 
  beuMiininu: 
  the 
  study 
  of 
  tin' 
  algffi 
  it 
  is 
  often 
  better 
  to 
  use 
  a 
  good 
  

   specimen 
  under 
  a 
  demonstration 
  mirrosro]te 
  than 
  to 
  attempt 
  individual 
  

   microscopic 
  work. 
  If 
  preceded 
  by 
  preliminary 
  demonstration 
  work 
  the 
  fol- 
  

   lowing 
  individual 
  studies 
  will 
  be 
  more 
  intelligible 
  and 
  successful. 
  

  

  