﻿8 
  

  

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

  

  characteristically 
  met 
  with 
  in 
  the 
  stem, 
  but 
  it 
  has 
  also 
  been 
  observed 
  in 
  

   many 
  roots 
  — 
  subterranean, 
  aerial, 
  and 
  aquatic 
  (e.g., 
  Stratiotes, 
  Plate 
  1, 
  fig. 
  29). 
  

   It- 
  occurs 
  in 
  many 
  leaf 
  structures, 
  such 
  as 
  the 
  sheathing 
  leaf 
  bases 
  of 
  a 
  

   number 
  of 
  grasses 
  (e.g., 
  Zea, 
  Plate 
  1, 
  fig. 
  3, 
  and 
  Avena, 
  Plate 
  1, 
  fig. 
  18) 
  and 
  

   in 
  the 
  basal 
  zone 
  of 
  the 
  perianth 
  of 
  Crocus. 
  We 
  have 
  frequently 
  met 
  with 
  

   binucleate 
  cells 
  in 
  the 
  cotyledon, 
  plumular 
  leaf, 
  mesocotyl 
  and 
  hypocotyl 
  

   of 
  seedlings. 
  The 
  range 
  of 
  tissues 
  concerned 
  is 
  also 
  very 
  wide, 
  including 
  

   pith, 
  cortex, 
  epidermis 
  and 
  stele 
  of 
  stem, 
  mesophyll 
  of 
  leaf, 
  cortex 
  and 
  stele 
  

   of 
  root. 
  

  

  In 
  all 
  the 
  cases 
  in 
  which 
  we 
  have 
  observed 
  multinucleate 
  cells, 
  they 
  are 
  

   characteristic 
  of 
  young 
  tissues 
  which 
  are 
  actively 
  carrying 
  on 
  the 
  processes 
  

   of 
  life. 
  For 
  example, 
  in 
  the 
  stem 
  the 
  multinucleate 
  cells 
  first 
  appear 
  in 
  a 
  

   region 
  just 
  behind 
  the 
  -actual 
  meristematic 
  tissue, 
  where 
  preparation 
  is 
  being 
  

   made 
  for 
  the 
  growth 
  in 
  length 
  of 
  the 
  organ. 
  In 
  Helianthus 
  Nuttallii 
  and 
  

   Syringa 
  vulgaris 
  binucleate 
  cells 
  make 
  their 
  first 
  appearance 
  01 
  mm. 
  behind 
  

   the 
  stem 
  apex. 
  

  

  In 
  those 
  stems 
  which 
  have 
  active 
  tissue, 
  capable 
  of 
  carrying 
  out 
  processes 
  

   of 
  growth, 
  situated 
  at 
  the 
  nodes 
  (such 
  as 
  the 
  stems 
  of 
  G-ramineee 
  and 
  of 
  

   Tradescantia) 
  the 
  multinucleate 
  cells 
  occur 
  predominantly 
  at 
  these 
  spots. 
  

  

  The 
  existence 
  of 
  the 
  multinucleate 
  phase 
  is 
  very 
  easily 
  demonstrated. 
  If 
  

   for 
  instance, 
  sections 
  be 
  made 
  across 
  the 
  " 
  heads 
  " 
  of 
  Asparagus, 
  at 
  the 
  stage 
  at 
  

   which 
  they 
  are 
  cut 
  for 
  market, 
  preparations 
  such 
  as 
  those 
  shown 
  in 
  text- 
  

   figs. 
  1 
  and 
  2 
  will 
  be 
  invariably 
  obtained. 
  

  

  The 
  number 
  of 
  nuclei 
  present 
  in 
  a 
  multinucleate 
  cell 
  varies 
  greatly 
  in 
  

   different 
  species. 
  Most 
  frequently 
  the 
  cells 
  are 
  binucleate, 
  but 
  in 
  many 
  cases 
  

   three, 
  four, 
  or 
  even 
  more 
  nuclei 
  may 
  occur 
  in 
  a 
  cell. 
  In 
  the 
  tissues 
  just 
  

   above 
  a 
  node 
  in 
  the 
  stem 
  of 
  Zea 
  Mays 
  (Plate 
  1, 
  fig. 
  4) 
  as 
  many 
  as 
  12 
  nuclei 
  

   may 
  sometimes 
  be 
  counted 
  in 
  a 
  single 
  cell, 
  whilst 
  in 
  the 
  young 
  inflorescence 
  

   axis 
  of 
  Anthriscus 
  sylvestris, 
  cells 
  containing 
  8, 
  9, 
  and 
  10 
  nuclei 
  are 
  not 
  

   uncommon 
  (e.g., 
  Plate 
  1, 
  fig. 
  13). 
  

  

  The 
  Origin 
  of 
  the 
  Multinucleate 
  Phase. 
  

  

  Nearly 
  all 
  previous 
  writers 
  have 
  been 
  agreed 
  in 
  holding 
  the 
  view 
  that 
  

   the 
  origin 
  of 
  the 
  multinucleate 
  condition 
  in 
  a 
  cell 
  is 
  due 
  to 
  the 
  amitotic 
  

   division 
  of 
  the 
  originally 
  single 
  nucleus. 
  Johow, 
  Strasburger, 
  Grant, 
  

   McLean 
  and 
  Prankerd 
  have 
  all 
  expressed 
  this 
  opinion 
  ; 
  Smolak 
  and 
  

   Nemec 
  are 
  almost 
  alone 
  in 
  having 
  observed 
  a 
  definite 
  instance 
  in 
  which 
  

   plurality 
  of 
  nuclei 
  became 
  established 
  in 
  the 
  cell 
  by 
  the 
  karyokinetic 
  division 
  

   of 
  the 
  primary 
  nucleus. 
  They 
  found 
  this 
  to 
  be 
  the 
  case 
  in 
  the 
  plerome 
  cells 
  

  

  