﻿Genetic 
  Segregation. 
  

  

  367 
  

  

  stem, 
  petioles, 
  and 
  (basal) 
  centres 
  of 
  the 
  leaves 
  without 
  chlorophyll.* 
  The 
  

   growing 
  point 
  has 
  the 
  power 
  of 
  laying 
  down 
  green 
  tissue 
  in 
  the 
  lateral 
  

   areas 
  only, 
  the 
  internodal 
  regions 
  being 
  albinotic. 
  Root-cuttings 
  from 
  this 
  

   form 
  give 
  albino 
  plants 
  which 
  die 
  after 
  the 
  development 
  of 
  two 
  or 
  three 
  

   small 
  leaves. 
  Now 
  in 
  this 
  case 
  we 
  can 
  see 
  the 
  distribution 
  of 
  the 
  green 
  

   and 
  white 
  respectively, 
  and 
  we 
  recognise 
  that 
  the 
  roots 
  give 
  albino 
  plants 
  

   because 
  they 
  belong 
  wholly 
  to 
  the, 
  albinotic 
  area. 
  On 
  similar 
  lines 
  it 
  is 
  

   possible 
  to 
  interpret 
  the 
  Bouvardia 
  and 
  other 
  cases. 
  The 
  distribution 
  of 
  

   the 
  two 
  types 
  in 
  the 
  same 
  plant 
  may 
  be 
  such 
  that 
  one 
  is 
  limited 
  to 
  the 
  

   root 
  and 
  internodes, 
  while 
  the 
  other 
  is 
  in 
  the 
  nodal 
  structures. 
  

  

  That 
  considerations 
  of 
  this 
  kind 
  are 
  not 
  fantastical 
  is 
  proved 
  by 
  the 
  

   genetical 
  phenomena 
  seen 
  in 
  the 
  case 
  of 
  " 
  rogues 
  " 
  in 
  culinary 
  peas, 
  which 
  

   Miss 
  fellew 
  and 
  I 
  have 
  been 
  investigating 
  for 
  a 
  number" 
  of 
  years, 
  f 
  The 
  

   rogue 
  is 
  a 
  peculiar, 
  wild-looking 
  plant, 
  differing 
  in 
  various 
  ways 
  from 
  the 
  

   type, 
  chiefly 
  in 
  having 
  pointed 
  leaflets. 
  Crosses 
  between 
  it 
  and 
  the 
  type 
  

   give 
  plants 
  which 
  in 
  their 
  lower 
  parts 
  are 
  intermediate, 
  though 
  turning 
  into 
  

   rogues 
  as 
  they 
  develop. 
  The 
  self-fertilised 
  offspring 
  of 
  rogues 
  and 
  also 
  of 
  

   these 
  Fx 
  plants 
  are 
  always 
  rogues, 
  and 
  evidently 
  the 
  type-characters 
  intro- 
  

   duced 
  from 
  the 
  type 
  parent 
  are 
  left 
  behind 
  in 
  the 
  lower 
  parts. 
  Such 
  a 
  case 
  

   may 
  perhaps 
  be 
  compared 
  with 
  the 
  condition 
  seen 
  in 
  the 
  variegated 
  Spiraea, 
  

   and 
  we 
  may 
  fairly 
  conjecture 
  that 
  if 
  it 
  were 
  possible 
  to 
  raise 
  root-cuttings 
  

   from 
  the 
  Fj 
  peas, 
  they 
  would 
  produce 
  types. 
  

  

  A 
  more 
  gradual 
  exclusion 
  of 
  the 
  type-elements 
  in 
  the 
  lower 
  parts 
  is 
  seen 
  in 
  

   certain 
  intermediates. 
  These 
  may 
  scarcely 
  differ 
  from 
  types 
  in 
  the 
  lower 
  

   parts, 
  though 
  changing 
  to 
  rogues, 
  sometimes 
  abruptly, 
  sometimes 
  gradually, 
  

   as 
  the 
  series 
  of 
  flowering 
  nodes 
  is 
  developed. 
  Reciprocal 
  crosses 
  between 
  the 
  

   successive 
  flowers 
  of 
  such 
  plants 
  and 
  the 
  flowers 
  of 
  types 
  has 
  shown 
  that, 
  

   together 
  with 
  the 
  gradational 
  change 
  in 
  the 
  somatic 
  structures, 
  there 
  is 
  also 
  a 
  

   gradational 
  change 
  in 
  the 
  proportion 
  of 
  gametes 
  bearing 
  the 
  rogue 
  and 
  type 
  

   characters 
  respectively. 
  This 
  proportion 
  and 
  the 
  rapidity 
  of 
  the 
  change 
  

   differ 
  on 
  the 
  male 
  and 
  female 
  sides. 
  Of 
  the 
  egg 
  cells 
  in 
  the 
  lower 
  flowers, 
  up 
  

   to 
  about 
  the 
  10th 
  flowering 
  node, 
  rather 
  more 
  than 
  50 
  per 
  cent, 
  carry 
  the 
  

   type-characters 
  — 
  or 
  at 
  least 
  the 
  non-pointed 
  leaflets 
  — 
  but 
  above 
  this 
  level 
  the 
  

   proportion 
  of 
  types 
  declines. 
  Of 
  the 
  pollen 
  in 
  the 
  lowest 
  two 
  flowers 
  only 
  

  

  * 
  This 
  is 
  .somewhat 
  like 
  the 
  Pelargonium 
  named 
  by 
  Messrs. 
  Cannell 
  " 
  Freak 
  of 
  

   Nature," 
  in 
  which 
  the 
  chlorophyll 
  has 
  a 
  closely 
  similar 
  distribution, 
  and 
  it, 
  like 
  the 
  

   Spircea, 
  is 
  sterile 
  on 
  both 
  male 
  and 
  female 
  sides. 
  In 
  this 
  Spircea 
  I 
  have 
  never 
  seen 
  

   pollen, 
  but 
  very 
  rarely 
  a 
  fruit 
  is 
  formed, 
  which, 
  no 
  doubt, 
  is 
  due 
  to 
  an 
  occasional 
  

   development 
  of 
  a 
  bud 
  in 
  the 
  green 
  area, 
  an 
  occurrence 
  frequent 
  in 
  variegated 
  plants. 
  

   Whether 
  these 
  fruits 
  contain 
  viable 
  seeds 
  is 
  not 
  yet 
  known. 
  

  

  t 
  'Boy. 
  Soc. 
  Proc.,' 
  E, 
  vol. 
  91, 
  p. 
  186 
  (192C). 
  

  

  VOL. 
  XCI. 
  — 
  B. 
  2 
  G 
  

  

  