﻿Stability 
  and 
  Real 
  Atavism 
  157 
  

  

  ly 
  impressed 
  with 
  its 
  absolute 
  constancy 
  and 
  its 
  

   behavior 
  as 
  an 
  ordinary 
  species, 
  that 
  they 
  have 
  

   elevated 
  it, 
  as 
  it 
  is 
  called, 
  to 
  the 
  rank 
  of 
  a 
  spe- 
  

   cies. 
  As 
  such 
  it 
  is 
  described 
  under 
  the 
  name 
  of 
  

   Matricaria 
  discoidea 
  DC. 
  It 
  is 
  remarkable 
  

   for 
  its 
  rapid 
  and 
  widespread 
  distribution, 
  as 
  of 
  

   late 
  years 
  it 
  has 
  become 
  naturalized 
  in 
  different 
  

   parts 
  of 
  America 
  and 
  of 
  Europe, 
  where 
  it 
  is 
  to 
  

   be 
  seen 
  especially 
  in 
  France 
  and 
  in 
  Norway. 
  

   Experimentally 
  I 
  raised 
  in 
  succeeding 
  years 
  be- 
  

   tween 
  1000 
  and 
  2000 
  seedlings, 
  but 
  observed 
  no 
  

   trace 
  of 
  reversion, 
  either 
  in 
  the 
  strongest 
  or 
  in 
  

   the 
  numerous 
  very 
  small 
  and 
  weak 
  individuals 
  

  

  \f 
  

  

  which 
  appeared 
  in 
  the 
  cultures. 
  

  

  The 
  tansy-ragwort 
  or 
  Senecio 
  Jacobaea 
  may 
  

   be 
  chosen 
  as 
  a 
  second 
  instance. 
  It 
  is 
  a 
  per- 
  

   ennial 
  herb 
  with 
  short 
  rootstocks 
  and 
  stout 
  

   stems 
  bearing 
  numerous 
  short-peduncled 
  heads 
  

   in 
  a 
  large 
  compact 
  corymb; 
  it 
  multiplies 
  itself 
  

   abundantly 
  by 
  seeds 
  and 
  is 
  very 
  common 
  on 
  

   the 
  sand 
  dimes 
  of 
  Holland. 
  It 
  has 
  two 
  forms, 
  

   differing 
  only 
  in 
  the 
  occurrence 
  or 
  the 
  lack 
  of 
  

   the 
  ray 
  florets. 
  But 
  these 
  two 
  varieties 
  occupy 
  

   different 
  localities 
  and 
  are 
  even 
  limited 
  to 
  dif- 
  

   ferent 
  provinces. 
  As 
  far 
  as 
  I 
  have 
  been 
  able 
  to 
  

   ascertain 
  on 
  numerous 
  excursions 
  during 
  a 
  

   series 
  of 
  years, 
  they 
  never 
  sport, 
  and 
  are 
  only 
  

   intermingled 
  on 
  the 
  outskirts 
  of 
  their 
  habitats. 
  

   The 
  rayless 
  form 
  is 
  generally 
  considered 
  as 
  the 
  

  

  