﻿NATURAL 
  RUBBER 
  — 
  COOK 
  377 
  

  

  GENERA 
  RELATED 
  TO 
  CAST1LLA 
  

  

  Several 
  genera 
  related 
  to 
  Costilla 
  are 
  worthy 
  of 
  being 
  canvassed 
  as 
  

   rubber 
  trees, 
  in 
  view 
  of 
  reports 
  by 
  botanical 
  collectors 
  that 
  the 
  latex 
  

   was 
  abundant 
  and 
  formed 
  an 
  elastic 
  substance. 
  Thus 
  Olmedia 
  aspera 
  

   and 
  0. 
  laevis 
  were 
  noted 
  by 
  Kuiz 
  in 
  1784 
  at 
  Pozuzo 
  on 
  the 
  eastern 
  

   slope 
  of 
  Peru 
  as 
  "trees 
  that 
  on 
  incision 
  give 
  an 
  abundance 
  of 
  very 
  

   white 
  milk, 
  which, 
  exposed 
  to 
  the 
  air, 
  turns 
  into 
  a 
  very 
  elastic 
  resin 
  of 
  a 
  

   reddish-chestnut 
  color; 
  it 
  can 
  be 
  shaped 
  into 
  any 
  form 
  desired." 
  The 
  

   presence 
  of 
  rubber 
  may 
  explain 
  a 
  statement 
  by 
  Sandeman 
  in 
  "A 
  For- 
  

   gotten 
  Kiver," 
  that 
  a 
  waterproof 
  bark 
  cloth 
  is 
  obtained 
  from 
  this 
  

   Olmedia, 
  which 
  the 
  Indians 
  call 
  llanchuma. 
  A 
  species 
  of 
  Perebea 
  in 
  

   Panama 
  was 
  described 
  by 
  James 
  Collins 
  as 
  Castilla 
  markamiana, 
  and 
  

   shares 
  the 
  native 
  name 
  ule 
  with 
  Castilla 
  panamensis. 
  Some 
  of 
  the 
  

   Brazilian 
  trees 
  referred 
  to 
  Helicostylis 
  have 
  a 
  notable 
  similarity 
  to 
  

   Castilla 
  ulei. 
  

  

  GENERA 
  RELATED 
  TO 
  PARA 
  RUBBER 
  

  

  Another 
  rubber-bearing 
  genus 
  in 
  South 
  America, 
  closely 
  related 
  to 
  

   the 
  Para 
  rubber 
  tree, 
  was 
  described 
  by 
  Bentham 
  under 
  the 
  name 
  Mi- 
  

   crandra. 
  It 
  seems 
  to 
  be 
  widely 
  distributed 
  in 
  South 
  America, 
  but 
  

   apparently 
  has 
  not 
  been 
  found 
  in 
  sufficient 
  abundance 
  for 
  commercial 
  

   exploitation. 
  Spruce 
  used 
  the 
  name 
  Muranda 
  for 
  this 
  genus, 
  of 
  which 
  

   he 
  saw 
  two 
  species 
  on 
  a 
  tributary 
  of 
  the 
  Rio 
  Negro, 
  differing 
  notably 
  

   from 
  the 
  Para 
  rubber 
  tree 
  in 
  their 
  simple 
  leaves 
  and 
  clustered 
  trunks, 
  

   "often 
  as 
  many 
  as 
  ten 
  from 
  a 
  root." 
  They 
  were 
  said 
  to 
  yield 
  "pure 
  

   rubber." 
  

  

  Several 
  South 
  American 
  rubber 
  trees 
  belong 
  to 
  the 
  genus 
  Sapiu?n, 
  

   also 
  a 
  member 
  of 
  the 
  spurge 
  family. 
  Some 
  of 
  the 
  sapiums 
  grow 
  at 
  

   rather 
  high 
  altitudes 
  in 
  the 
  Andes, 
  6,000 
  to 
  8,000 
  feet, 
  and 
  produce 
  

   what 
  has 
  long 
  been 
  known 
  as 
  "virgin 
  rubber," 
  some 
  of 
  it 
  reputed 
  to 
  

   be 
  of 
  excellent 
  quality. 
  Other 
  species 
  grow 
  in 
  the 
  Amazon 
  valley 
  and 
  

   are 
  reported 
  to 
  share 
  the 
  habits 
  of 
  the 
  Para 
  rubber 
  tree 
  and 
  to 
  yield 
  

   latex 
  in 
  the 
  same 
  manner, 
  by 
  the 
  native 
  method 
  of 
  making 
  many 
  wounds 
  

   with 
  small 
  hatchets. 
  This 
  may 
  mean 
  that 
  the 
  latex 
  tubes 
  of 
  Sapiwm 
  

   form 
  a 
  continuous 
  network 
  as 
  in 
  the 
  Para 
  rubber. 
  A 
  plantation 
  of 
  

   70,000 
  Sapium 
  trees 
  was 
  reported 
  from 
  Colombia 
  in 
  1888 
  as 
  "growing 
  

   with 
  great 
  rapidity, 
  and 
  averaging 
  about 
  five 
  feet 
  a 
  year," 
  according 
  to 
  

   a 
  letter 
  published 
  in 
  the 
  Kew 
  Bulletin 
  of 
  1906. 
  

  

  EVALUATION 
  OF 
  RUBBER 
  TREES 
  

  

  The 
  rubber 
  planter 
  encounters 
  the 
  problems 
  of 
  choosing 
  favorable 
  

   natural 
  conditions, 
  devising 
  suitable 
  cultural 
  methods, 
  and 
  selecting 
  

  

  