﻿NATURAL 
  RUBBER 
  — 
  COOK 
  393 
  

  

  ences 
  in 
  adaptive 
  characters 
  between 
  the 
  Castilla 
  and 
  the 
  Para 
  rubber 
  

   tree 
  emphasize 
  the 
  need 
  for 
  critical 
  comparison 
  of 
  the 
  cultural 
  require- 
  

   ments 
  of 
  the 
  two 
  trees. 
  

  

  BRANCHING 
  HABITS 
  OF 
  PARA 
  RUBBER 
  TREE 
  

  

  As 
  a 
  consequence 
  of 
  the 
  habits 
  of 
  branching 
  in 
  the 
  Para 
  rubber 
  

   tree, 
  two 
  distinct 
  phases 
  of 
  growth 
  may 
  be 
  recognized: 
  a 
  juvenile 
  

   phase 
  that 
  includes 
  the 
  development 
  of 
  a 
  simple 
  primary 
  upright, 
  

   and 
  an 
  adult 
  phase 
  that 
  comprises 
  the 
  subsequent 
  growth 
  of 
  the 
  

   tree, 
  after 
  the 
  formation 
  of 
  branches. 
  The 
  pattern 
  of 
  growth 
  in 
  

   the 
  young 
  tree 
  is 
  characterized 
  by 
  the 
  suppression 
  of 
  lateral 
  buds 
  

   in 
  all 
  the 
  joints 
  of 
  the 
  trunk, 
  which 
  results 
  in 
  the 
  formation 
  of 
  a 
  

   tall, 
  simple 
  trunk 
  as 
  rapidly 
  as 
  possible; 
  in 
  the 
  adult 
  phase 
  many 
  

   diverging 
  branches 
  are 
  formed, 
  and 
  the 
  upward 
  growth 
  of 
  the 
  trunk 
  

   to 
  form 
  a 
  central 
  axis 
  of 
  the 
  tree 
  is 
  discontinued. 
  

  

  Although 
  the 
  branching 
  of 
  individual 
  Para 
  rubber 
  trees 
  is 
  ex- 
  

   tremely 
  variable, 
  there 
  is 
  a 
  notable 
  tendency 
  to 
  form 
  a 
  cluster 
  or 
  

   whorl 
  of 
  branches 
  at 
  the 
  end 
  of 
  the 
  primary 
  upright, 
  so 
  that 
  many 
  

   of 
  the 
  trees 
  have 
  the 
  form 
  of 
  a 
  brush 
  or 
  candelabrum. 
  In 
  exposed 
  

   places, 
  where 
  the 
  trees 
  are 
  checked 
  or 
  stunted, 
  the 
  branching 
  pattern 
  

   is 
  often 
  disturbed, 
  and 
  a 
  few 
  branches 
  are 
  formed 
  along 
  the 
  trunks, 
  

   usually 
  as 
  singles 
  or 
  pairs, 
  before 
  a 
  normal 
  whorl 
  of 
  branches 
  is 
  

   produced 
  ; 
  or 
  the 
  branching 
  pattern 
  may 
  remain 
  irregular. 
  

  

  INTERMITTENT 
  GROWTH 
  OF 
  TRUNK 
  

  

  The 
  pattern 
  of 
  branching 
  undoubtedly 
  has 
  a 
  relation 
  to 
  the 
  mode 
  

   of 
  development 
  of 
  the 
  trunk, 
  by 
  flushes 
  or 
  spurts 
  of 
  growth. 
  Each 
  

   period 
  of 
  activity 
  results 
  in 
  the 
  formation 
  of 
  a 
  new 
  section 
  of 
  the 
  

   trunk, 
  composed 
  of 
  numerous 
  joints 
  of 
  different 
  lengths. 
  The 
  ter- 
  

   minal 
  leaf-bearing 
  members 
  of 
  a 
  growth 
  section 
  are 
  much 
  shorter 
  

   than 
  the 
  basal 
  metamers, 
  which 
  often 
  are 
  without 
  leaves, 
  or 
  have 
  

   the 
  leaves 
  reduced 
  to 
  minute 
  hooklike 
  rudiments. 
  

  

  The 
  development 
  of 
  a 
  new 
  growth 
  section 
  is 
  very 
  rapid, 
  so 
  that 
  

   the 
  entire 
  whorl 
  of 
  leaves 
  is 
  produced 
  practically 
  simultaneously, 
  

   following 
  a 
  period 
  of 
  rest 
  when 
  the 
  terminal 
  bud 
  remains 
  completely 
  

   dormant. 
  Under 
  forest 
  conditions, 
  with 
  the 
  rubber 
  seedlings 
  re- 
  

   ceiving 
  little 
  light 
  and 
  competing 
  with 
  other 
  vegetation, 
  long 
  intervals 
  

   may 
  elapse, 
  perhaps 
  entire 
  seasons, 
  between 
  the 
  development 
  of 
  suc- 
  

   cessive 
  growth 
  sections. 
  

  

  It 
  is 
  not 
  difficult 
  to 
  see 
  that 
  the 
  habit 
  of 
  intermittent 
  growth 
  may 
  

   have 
  advantages 
  under 
  forest 
  conditions 
  where 
  light 
  is 
  deficient. 
  The 
  

   only 
  seedlings 
  that 
  can 
  be 
  expected 
  to 
  develop 
  on 
  the 
  floor 
  of 
  the 
  deep 
  

   forest 
  are 
  those 
  that 
  live 
  with 
  very 
  little 
  light. 
  The 
  chance 
  of 
  reach- 
  

  

  