﻿12 
  

  

  Mr. 
  R. 
  Beer 
  and 
  Dr. 
  A. 
  Arber. 
  On 
  the 
  

  

  The 
  Fate 
  of 
  the 
  Nuclei. 
  

  

  The 
  fate 
  of 
  the 
  nuclei 
  in 
  multinucleate 
  cells 
  varies 
  in 
  the 
  different 
  species. 
  

  

  In 
  some 
  cases, 
  the 
  plurality 
  of 
  nuclei 
  may 
  persist 
  to 
  a 
  late 
  stage. 
  Thus 
  

   in 
  the 
  stem 
  of 
  Syringa 
  vulgaris 
  binucleate 
  cells 
  still 
  occur 
  in 
  the 
  perime- 
  

   dullary 
  zone 
  as 
  far 
  as 
  93 
  cm. 
  from 
  the 
  apex, 
  whilst 
  in 
  Rosa 
  binucleate 
  cells 
  

   were 
  still 
  seen 
  in 
  the 
  cortex 
  of 
  a 
  two-year 
  old 
  stem 
  (Plate 
  1, 
  fig. 
  17). 
  

  

  In 
  other 
  cases 
  one 
  or 
  more 
  of 
  the 
  nuclei 
  may 
  undergo 
  degeneration 
  {e.g., 
  

   Zea 
  Mays, 
  Plate 
  1, 
  fig. 
  6). 
  This 
  can 
  be 
  well 
  seen 
  in 
  the 
  flowering 
  axis 
  of 
  

   Hemerocallis 
  fulva. 
  In 
  material 
  gathered 
  on 
  May 
  21 
  and 
  24 
  (1916) 
  the 
  ' 
  

   region 
  of 
  the 
  axis 
  just 
  below 
  the 
  base 
  of 
  the 
  young 
  inflorescence 
  showed 
  

   numerous 
  cases 
  of 
  cells 
  in 
  which 
  one 
  nucleus 
  was 
  normal, 
  while 
  the 
  second 
  

   was 
  obviously 
  degenerating. 
  The 
  degenerating 
  nuclei 
  are 
  contracted 
  and 
  

   irregular 
  in 
  form 
  ; 
  they 
  seem 
  to 
  be 
  structureless, 
  since 
  they 
  stain 
  more 
  or 
  less 
  

   homogeneously, 
  while 
  the 
  normal 
  nuclei 
  accompanying 
  them 
  are 
  granular 
  in 
  

   appearance 
  with 
  a 
  number 
  of 
  nucleoli. 
  Further 
  down 
  the 
  axis 
  the 
  cells 
  are 
  

   mostly 
  uninucleate. 
  

  

  Although 
  we 
  have 
  spent 
  much 
  time 
  on 
  the 
  matter, 
  no 
  instances 
  of 
  nuclear 
  

   fusions, 
  as 
  factors 
  in 
  the 
  reduction 
  of 
  the 
  number 
  of 
  the 
  nuclei, 
  have 
  been 
  

   observed. 
  Neither 
  has 
  any 
  evidence 
  been 
  forthcoming 
  of 
  the 
  existence 
  of 
  a 
  

   belated 
  cell-division 
  leading 
  to 
  the 
  separation 
  of 
  the 
  nuclei 
  of 
  a 
  multinucleate 
  

   cell 
  by 
  the 
  interpolation 
  of 
  new 
  cell 
  walls 
  between 
  them. 
  Lobed 
  nuclei 
  have 
  

   been 
  observed 
  in 
  several 
  instances, 
  e.g., 
  Helmintlwstachys, 
  Plate 
  1, 
  fig. 
  24, 
  

   but 
  a 
  careful 
  and 
  critical 
  examination 
  of 
  these 
  cases 
  has 
  convinced 
  us 
  that 
  

   these 
  have 
  neither 
  the 
  significance 
  of 
  nuclear 
  fusions 
  nor 
  of 
  amitotic 
  

   divisions. 
  They 
  merely 
  represent 
  a 
  change 
  of 
  form 
  which 
  is 
  the 
  expression 
  

   of 
  metabolic 
  activities 
  taking 
  place 
  in 
  the 
  cell. 
  Statiotes 
  aloides* 
  Asparagus 
  

   officinalis, 
  and 
  Tradescantia 
  virginiana 
  furnish 
  instances 
  of 
  such 
  lobed 
  nuclei. 
  

  

  The 
  case 
  of 
  Tradescantia 
  is 
  particularly 
  noteworthy, 
  since 
  it 
  has 
  long 
  been 
  

   regarded 
  as 
  one 
  of 
  the 
  classical 
  instances 
  of 
  nuclear 
  amitosis 
  in 
  the 
  higher- 
  

   plants. 
  We 
  have, 
  however, 
  found 
  unmistakable 
  evidence 
  that 
  the 
  plurality 
  

   of 
  nuclei 
  in 
  the 
  stems 
  of 
  this 
  plant 
  arises 
  by 
  mitotic 
  division 
  accompanied 
  

   by 
  the 
  occurrence 
  of 
  characteristic 
  phragmospheres. 
  The 
  lobing 
  of 
  the 
  

   nuclei 
  is 
  here, 
  as 
  elsewhere, 
  a 
  mere 
  change 
  of 
  form, 
  which 
  rarely 
  if 
  ever 
  bears 
  

   any 
  relation 
  to 
  their 
  multiplication. 
  

  

  After 
  our 
  work 
  on 
  Tradescantia 
  was 
  completed, 
  a 
  recent 
  paper 
  by 
  

  

  * 
  In 
  a 
  former 
  paper 
  by 
  one 
  of 
  us 
  (Arber, 
  A., 
  ' 
  Proc. 
  Canib. 
  Phil. 
  Soc.,' 
  vol. 
  17, 
  p. 
  369 
  

   (1914)), 
  the 
  origin 
  of 
  the 
  binucleate 
  phase 
  in 
  the 
  roots 
  of 
  Stratiotes 
  was 
  wrongly 
  

   attributed 
  to 
  amitosis. 
  Further 
  work 
  has 
  shown 
  that 
  the 
  binucleate 
  condition 
  arises 
  

   by 
  karyokinesis 
  accompanied 
  by 
  phragmosphere 
  formation'(Plate 
  1, 
  fig. 
  29), 
  and 
  that 
  the 
  

   lobing 
  is 
  a 
  distinct 
  phenomenon. 
  

  

  