﻿Studies 
  in 
  the 
  conjugation 
  of 
  Spirogyra 
  ternata 
  

  

  Mabel 
  L. 
  Merriman 
  

  

  (with 
  three 
  text 
  figures) 
  

  

  The 
  discovery 
  of 
  but 
  four 
  chromosomes 
  in 
  Spirogyra 
  ternata 
  

   led 
  to 
  the 
  collection 
  of 
  material 
  in 
  fruiting 
  condition 
  during 
  the 
  

   months 
  of 
  October 
  and 
  November, 
  1915 
  and 
  1916. 
  The 
  alga 
  was 
  

   growing 
  under 
  more 
  or 
  less 
  unnatural 
  conditions 
  in 
  a 
  basin 
  where 
  

   the 
  water 
  was 
  drawn 
  oflF 
  during 
  the 
  winter 
  months- 
  Its 
  continued 
  

   propagation 
  seems 
  uncertain 
  as 
  no 
  trace 
  of 
  it 
  was 
  found 
  in 
  the 
  fall 
  

  

  of 
  1917 
  or 
  1918. 
  

  

  The 
  large 
  size 
  of 
  the 
  nuclei, 
  the 
  low 
  number 
  of 
  chromosomes, 
  

   the 
  few 
  chromatophores, 
  and 
  the 
  general 
  transparency 
  of 
  the 
  

   cells, 
  combined 
  with 
  marked 
  sexual 
  differentiation 
  of 
  the 
  filaments 
  

   in 
  conjugating 
  periods, 
  are 
  features 
  that 
  make 
  this 
  species 
  especially 
  

   favorable 
  material 
  for 
  the 
  investigation 
  of 
  such 
  debated 
  questions 
  

  

  I 
  ' 
  

  

  as 
  the 
  potential 
  bisexuality 
  of 
  vegetative 
  cells, 
  chromosome 
  

   reduction, 
  and 
  the 
  history 
  of 
  the 
  secondary 
  nuclei 
  in 
  the 
  sporo- 
  

   phyte 
  generation. 
  While 
  material 
  was 
  at 
  first 
  studied 
  with 
  the 
  

   hope 
  of 
  elucidation 
  of 
  these 
  problems, 
  continued 
  study 
  of 
  the 
  

   filaments 
  brought 
  to 
  light 
  interesting 
  changes 
  in 
  the 
  cells 
  as 
  they 
  

   pass 
  from 
  the 
  vegetative 
  condition 
  to 
  a 
  state 
  of 
  conjugation. 
  

  

  The 
  diagnostic 
  features 
  of 
  S. 
  ternata 
  Ripart 
  (1876), 
  as 
  described 
  

  

  50-65 
  

  

  3^2 
  

  

  45-66 
  )u 
  In 
  diameter, 
  i-i3^ 
  diameters 
  long. 
  

  

  The 
  form 
  collected 
  in 
  1915 
  varied 
  from 
  this 
  in 
  having 
  its 
  

   vegetative 
  cells 
  74-80 
  m 
  in 
  width. 
  The 
  zygospores 
  in 
  this 
  191 
  5 
  

   material 
  measured 
  64 
  ju 
  in 
  width 
  and 
  120;! 
  in 
  length. 
  In 
  the 
  

   191 
  6 
  material 
  there 
  was 
  much 
  greater 
  variability 
  and 
  frequent 
  

   hybridization 
  with 
  a 
  larger 
  species 
  resembling 
  S. 
  jugalis 
  but 
  

   differing 
  in 
  the 
  shape 
  of 
  the 
  fertile 
  cell. 
  The 
  comparison 
  of 
  S. 
  

   ternata 
  with 
  another 
  species, 
  5. 
  maxima, 
  growing 
  under 
  the 
  same 
  

   conditions 
  and 
  fruiting 
  at 
  the 
  same 
  season, 
  revealed 
  such 
  great 
  

  

  9 
  

  

  