﻿NATURAL 
  RUBBER 
  — 
  COOK 
  397 
  

  

  the 
  individual 
  yields 
  still 
  vary 
  widely 
  on 
  account 
  of 
  diversity 
  of 
  the 
  

   stocks. 
  

  

  The 
  multifarious 
  individual 
  diversities 
  shown 
  in 
  these 
  disorders 
  

   are 
  of 
  potential 
  interest 
  and 
  significance 
  in 
  relation 
  to 
  heredity 
  and 
  

   evolution, 
  in 
  showing 
  that 
  great 
  numbers 
  of 
  different 
  patterns 
  of 
  di- 
  

   vergence 
  from 
  normal 
  heredity 
  are 
  set 
  up 
  and 
  consistently 
  followed 
  

   for 
  weeks, 
  months, 
  or 
  years 
  in 
  the 
  development 
  of 
  the 
  individual 
  

   plants. 
  These 
  individual 
  patterns 
  are 
  often 
  so 
  completely 
  different 
  in 
  

   closely 
  contiguous 
  plants 
  as 
  to 
  forbid 
  any 
  assumption 
  that 
  different 
  

   conditions 
  of 
  growth 
  explain 
  the 
  variations. 
  The 
  effects 
  of 
  local 
  

   conditions 
  or 
  injuries 
  may 
  be 
  seen 
  as 
  inducing 
  the 
  general 
  instability 
  

   in 
  the 
  expression 
  of 
  the 
  hereditary 
  characters 
  that 
  seems 
  also 
  to 
  occur 
  

   in 
  some 
  of 
  the 
  deficiency 
  diseases, 
  giving 
  rise 
  to 
  extremely 
  varied 
  

   symptoms. 
  

  

  DIVERSITY 
  IN 
  ABNORMAL 
  PLANTS 
  

  

  In 
  addition 
  to 
  the 
  variants 
  that 
  grow 
  with 
  nearly 
  normal 
  vigor, 
  

   there 
  are 
  great 
  numbers 
  of 
  seedlings 
  that 
  must 
  be 
  reckoned 
  as 
  defi- 
  

   nitely 
  abnormal. 
  Many 
  are 
  practically 
  leafless, 
  or 
  with 
  leaves 
  so 
  pale, 
  

   dwarfed, 
  and 
  distorted 
  that 
  the 
  plants 
  are 
  able 
  to 
  survive 
  only 
  while 
  

   protected 
  in 
  the 
  seed 
  beds. 
  

  

  Many 
  illustrations 
  would 
  be 
  required 
  to 
  show 
  the 
  range 
  of 
  diversities 
  

   in 
  the 
  various 
  characters, 
  but 
  the 
  three 
  given 
  in 
  plates 
  9 
  and 
  10 
  il- 
  

   lustrate 
  abnormally 
  narrow 
  leaves 
  of 
  different 
  forms. 
  A 
  rather 
  ex- 
  

   treme 
  form 
  is 
  shown 
  at 
  the 
  right 
  of 
  plate 
  9, 
  with 
  the 
  primary 
  veins 
  

   much 
  closer 
  and 
  more 
  numerous 
  than 
  those 
  of 
  normal 
  pinnae 
  shown 
  

   at 
  the 
  left 
  in 
  plate 
  10. 
  The 
  narrow, 
  tapering, 
  erect 
  pinnae 
  at 
  the 
  right 
  

   of 
  plate 
  10 
  have 
  little 
  resemblance 
  to 
  the 
  long, 
  drooping 
  pinnae 
  ol 
  

   plate 
  9. 
  Many 
  variants 
  have 
  still 
  narrower 
  pinnae, 
  with 
  the 
  margins 
  

   notched 
  to 
  the 
  midrib, 
  while 
  others 
  have 
  curved 
  or 
  twisted 
  pinnae, 
  or 
  

   funnel-shapel 
  "ascidia." 
  The 
  series 
  of 
  foliar 
  aberrations 
  is 
  compara- 
  

   ble 
  to 
  that 
  of 
  the 
  familiar 
  "crotons" 
  or 
  codiaeums, 
  which 
  also 
  belong 
  

   to 
  the 
  spurge 
  family. 
  Pinnae 
  of 
  normal 
  form 
  are 
  only 
  2 
  or 
  3 
  times 
  

   as 
  long 
  as 
  wide, 
  while 
  some 
  of 
  the 
  abnormal 
  pinnae 
  are 
  10 
  to 
  20 
  times 
  

   as 
  long 
  as 
  wide. 
  Some 
  abnormal 
  plants 
  have 
  the 
  stalks 
  of 
  the 
  pinnae 
  

   longer 
  than 
  usual, 
  or 
  the 
  stalks 
  may 
  be 
  very 
  short 
  and 
  grown 
  to- 
  

   gether, 
  so 
  that 
  the 
  pinnae 
  do 
  not 
  separate. 
  Some 
  leaves 
  exhibit 
  super- 
  

   numerary 
  pinnae. 
  

  

  RECOVERY 
  OF 
  NORMAL 
  LEAF 
  FORMS 
  

  

  A 
  notable 
  feature 
  of 
  these 
  abnormal 
  rubber 
  seedlings 
  is 
  that 
  sudden 
  

   and 
  striking 
  changes 
  toward 
  more 
  normal 
  leaf 
  patterns 
  and 
  growth 
  

   behavior 
  are 
  possible, 
  as 
  shown 
  in 
  plate 
  9. 
  A 
  plant 
  with 
  only 
  narrow, 
  

   slender 
  leaves 
  develops 
  a 
  new 
  cluster 
  with 
  its 
  leaves 
  of 
  normal, 
  or 
  

   nearly 
  normal, 
  proportions. 
  This 
  ability 
  to 
  recover 
  shows 
  that 
  the 
  

  

  