﻿NATURAL 
  RUBBER 
  — 
  COOK 
  395 
  

  

  series 
  of 
  leafless 
  metamers, 
  usually 
  three 
  to 
  five, 
  corresponding 
  to 
  

   the 
  leafless 
  metamers 
  below 
  the 
  first 
  leaves. 
  Thus 
  the 
  alternation 
  of 
  

   groups 
  of 
  leafless 
  and 
  leaf 
  -bearing 
  metamers 
  in 
  the 
  subsequent 
  devel- 
  

   opment 
  of 
  the 
  trunk 
  may 
  be 
  homologized 
  with 
  the 
  specializations 
  

   of 
  the 
  seedling. 
  

  

  In 
  the 
  later 
  development 
  of 
  the 
  tree 
  the 
  specialized 
  basal 
  metamer 
  

   of 
  the 
  seedling 
  appears 
  somewhat 
  distinct. 
  Often 
  this 
  section 
  is 
  rather 
  

   abruptly 
  thickened 
  in 
  advance 
  of 
  the 
  others, 
  and 
  the 
  enlargement 
  con- 
  

   tinues 
  in 
  many 
  trees 
  to 
  the 
  formation 
  of 
  salient 
  angles 
  or 
  buttresses 
  

   around 
  the 
  base 
  of 
  the 
  trunk. 
  The 
  production 
  of 
  adventitious 
  roots 
  

   from 
  the 
  surface 
  of 
  the 
  enlarged 
  basal 
  section 
  also 
  occurs 
  rather 
  fre- 
  

   quently, 
  especially 
  on 
  young 
  trees 
  that 
  stand 
  in 
  depressions 
  or 
  where 
  

   the 
  soil 
  is 
  deepened 
  by 
  top 
  dressing. 
  

  

  SPONGY, 
  PERISHABLE 
  SEEDS 
  

  

  The 
  seeds 
  of 
  the 
  Para 
  rubber 
  tree 
  are 
  very 
  similar 
  to 
  the 
  seeds 
  of 
  

   some 
  of 
  the 
  palms 
  that 
  are 
  specialized 
  for 
  forest 
  conditions. 
  There 
  

   is 
  a 
  thin 
  outer 
  shell 
  of 
  very 
  hard 
  columnar 
  tissue, 
  filled 
  with 
  the 
  rather 
  

   succulent, 
  loose-textured 
  cotyledons, 
  like 
  the 
  endosperm 
  of 
  some 
  of 
  

   the 
  forest 
  palms, 
  as 
  Oenocarpus 
  and 
  Astrocaryvm. 
  The 
  soft 
  texture 
  

   of 
  the 
  seeds 
  may 
  not 
  be 
  an 
  advantage 
  in 
  itself, 
  but 
  is 
  doubtless 
  due 
  

   to 
  the 
  fact 
  that 
  water 
  is 
  carried 
  in 
  the 
  tissue, 
  so 
  that 
  the 
  preliminaries 
  

   of 
  germination 
  can 
  go 
  forward 
  without 
  waiting 
  for 
  moisture 
  to 
  be 
  

   absorbed 
  from 
  the 
  outside. 
  Thus 
  it 
  is 
  possible 
  for 
  the 
  seeds 
  of 
  the 
  

   Para 
  rubber 
  tree 
  to 
  germinate 
  without 
  being 
  covered, 
  but 
  merely 
  

   lying 
  among 
  the 
  dead 
  leaves 
  or 
  on 
  the 
  surface 
  of 
  the 
  ground 
  under 
  

   the 
  forest 
  shade. 
  Germination 
  may 
  be 
  deferred 
  to 
  some 
  extent 
  if 
  the 
  

   seeds 
  are 
  kept 
  a 
  little 
  dry, 
  but 
  they 
  die 
  very 
  soon 
  if 
  drying 
  is 
  carried 
  

   too 
  far. 
  

  

  The 
  hard 
  shell 
  is 
  not 
  ruptured 
  in 
  the 
  germination 
  of 
  the 
  seed, 
  the 
  

   plumule, 
  carried 
  by 
  the 
  growth 
  of 
  the 
  petioles 
  of 
  the 
  cotyledons, 
  emerg- 
  

   ing 
  through 
  a 
  small 
  round 
  hole, 
  a 
  method 
  of 
  germination 
  that 
  is 
  fol- 
  

   lowed 
  in 
  many 
  palms. 
  As 
  soon 
  as 
  the 
  roots 
  are 
  exposed, 
  the 
  seedlings 
  

   can 
  absorb 
  moisture 
  from 
  wet 
  surfaces, 
  though 
  the 
  soft-textured 
  coty- 
  

   ledons, 
  protected 
  by 
  the 
  shell 
  of 
  the 
  seed, 
  may 
  continue 
  to 
  function 
  

   for 
  storing 
  and 
  equalizing 
  the 
  supply 
  of 
  water 
  until 
  the 
  roots 
  have 
  

   penetrated 
  to 
  permanent 
  moisture. 
  Having 
  made 
  its 
  contacts 
  with 
  

   the 
  soil, 
  the 
  Para 
  rubber 
  seedling 
  wastes 
  no 
  time 
  forming 
  leaves 
  near 
  

   the 
  ground, 
  but 
  sends 
  up 
  a 
  smooth, 
  slender, 
  green 
  stem, 
  sometimes 
  a 
  

   foot 
  long 
  before 
  producing 
  any 
  leaves. 
  

  

  LEAVES 
  OF 
  SEEDLINGS 
  DELICATE 
  

  

  The 
  delicate 
  texture 
  of 
  the 
  leaves 
  of 
  the 
  seedlings 
  is 
  another 
  forest 
  

   adaptation 
  that 
  seems 
  to 
  be 
  definitely 
  established 
  in 
  the 
  Para 
  rubber 
  

  

  