﻿380 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  can 
  be 
  stolen 
  by 
  thieves 
  and 
  the 
  trees 
  mutilated 
  by 
  severe 
  tapping, 
  

   whereas 
  the 
  Para 
  trees 
  have 
  little 
  interest 
  for 
  rubber 
  thieves. 
  Castilla 
  

   is 
  considered 
  beneficial 
  to 
  the 
  soil, 
  a 
  claim 
  also 
  made 
  for 
  several 
  of 
  the 
  

   tropical 
  fig 
  trees. 
  Coffee 
  and 
  cacao 
  grow 
  well 
  under 
  the 
  shade 
  of 
  

   Castilla 
  and 
  Para 
  rubber 
  trees. 
  Both 
  trees 
  have 
  an 
  annual 
  leaf 
  fall, 
  

   allowing 
  subcultures 
  a 
  few 
  weeks 
  of 
  sunlight. 
  

  

  People 
  who 
  live 
  in 
  these 
  tropical 
  gardens 
  have 
  an 
  initial 
  advantage 
  

   in 
  raising 
  their 
  rubber 
  trees 
  at 
  no 
  expense, 
  if 
  seeds 
  or 
  seedlings 
  are 
  

   available. 
  Little 
  room 
  is 
  required 
  for 
  the 
  young 
  rubber 
  trees, 
  which 
  

   are 
  very 
  slender 
  at 
  first, 
  and 
  interfere 
  very 
  little 
  with 
  other 
  uses 
  of 
  

   such 
  gardens. 
  In 
  addition 
  to 
  familiar 
  fruits 
  and 
  medicinal 
  trees, 
  

   many 
  useless 
  "wild" 
  trees 
  are 
  often 
  allowed 
  to 
  grow 
  in 
  and 
  around 
  the 
  

   tropical 
  gardens 
  and 
  small 
  farms, 
  for 
  protection 
  from 
  sun 
  and 
  wind. 
  

   If 
  only 
  the 
  useless 
  trees 
  in 
  native 
  gardens 
  of 
  tropical 
  America 
  were 
  

   replaced 
  by 
  Para 
  rubber 
  trees, 
  an 
  extensive 
  production 
  would 
  be 
  as- 
  

   sured, 
  possibly 
  more 
  than 
  from 
  plantations 
  in 
  tropical 
  America, 
  where 
  

   plantation 
  labor 
  is 
  difficult 
  to 
  obtain. 
  

  

  Local 
  supplies 
  of 
  seeds 
  or 
  seedlings 
  are 
  the 
  first 
  requirement 
  for 
  al- 
  

   lowing 
  the 
  Para 
  rubber 
  to 
  spread 
  widely 
  as 
  a 
  garden 
  crop 
  in 
  tropical 
  

   America. 
  The 
  seeds 
  have 
  hard 
  shells, 
  but 
  the 
  kernels 
  are 
  soft 
  and 
  

   perishable, 
  so 
  that 
  prompt 
  planting 
  is 
  necessary 
  unless 
  special 
  packing 
  

   and 
  handling 
  are 
  provided. 
  The 
  seeds 
  may 
  be 
  planted 
  "at 
  the 
  stake," 
  

   or 
  budded 
  seedlings 
  might 
  be 
  planted, 
  if 
  proper 
  care 
  is 
  used. 
  

  

  PROBLEMS 
  OF 
  RUBBER 
  LATEX 
  

  

  Many 
  theories 
  of 
  the 
  function 
  of 
  rubber 
  in 
  plants 
  have 
  been 
  ad- 
  

   vanced, 
  but 
  none 
  has 
  had 
  general 
  acceptance. 
  A 
  flow 
  of 
  latex 
  may 
  

   cover 
  a 
  wound, 
  but 
  many 
  plants 
  that 
  contain 
  rubber 
  do 
  not 
  form 
  

   latex. 
  Other 
  functions, 
  as 
  storage 
  or 
  transportation 
  of 
  water 
  or 
  food 
  

   materials, 
  may 
  be 
  performed 
  by 
  systems 
  of 
  latex 
  tubes, 
  apart 
  from 
  

   the 
  rubber 
  particles 
  that 
  the 
  latex 
  may 
  carry. 
  Rubber 
  is 
  not, 
  like 
  

   sugar, 
  starch, 
  or 
  cellulose, 
  to 
  be 
  viewed 
  as 
  a 
  convertible 
  storage 
  product 
  

   of 
  further 
  use 
  in 
  growth 
  or 
  tissue 
  building, 
  but 
  is 
  rather 
  to 
  be 
  segre- 
  

   gated 
  in 
  one 
  part 
  or 
  another, 
  the 
  bark, 
  the 
  leaves, 
  the 
  fruits, 
  or 
  the 
  

   roots 
  in 
  the 
  various 
  cases 
  that 
  are 
  known, 
  with 
  or 
  without 
  the 
  assistance 
  

   of 
  latex 
  tubes. 
  To 
  consider 
  rubber 
  as 
  a 
  waste 
  product 
  makes 
  more 
  

   understandable 
  its 
  occurrence 
  in 
  so 
  many 
  unrelated 
  plants, 
  and 
  in 
  so 
  

   many 
  different 
  tissues 
  of 
  the 
  plants 
  — 
  principally 
  the 
  bark, 
  leaves, 
  and 
  

   fruits. 
  The 
  tissues 
  that 
  are 
  discarded 
  are 
  likely 
  to 
  contain 
  more 
  

   rubber 
  than 
  those 
  that 
  remain 
  as 
  permanent 
  parts 
  of 
  the 
  plant 
  

   structure. 
  

  

  RUBBER 
  BY 
  RULE 
  OF 
  THUMB 
  

  

  In 
  any 
  latex-bearing 
  tree 
  or 
  plant 
  the 
  presence 
  or 
  absence 
  of 
  good 
  

   rubber 
  can 
  be 
  determined 
  by 
  an 
  extremely 
  simple 
  test 
  made 
  with 
  the 
  

  

  