﻿INTRODUCTORY 
  

  

  Tf 
  plant 
  production 
  were 
  not 
  so 
  important 
  to 
  the 
  world, 
  there 
  

   would 
  be 
  little 
  need 
  of 
  having 
  domesticated 
  animals. 
  Our 
  

  

  FIG. 
  2. 
  Dense 
  vegetation 
  as 
  seen 
  in 
  a 
  tropical 
  forest 
  

  

  During 
  the 
  relatively 
  dry 
  season, 
  water 
  may 
  cease 
  flowing 
  in 
  the 
  stream 
  bed 
  

   here 
  shown, 
  but 
  even 
  then 
  almost 
  all 
  available 
  space 
  is 
  occupied 
  by 
  plants. 
  Dur- 
  

   ing 
  wet 
  seasons 
  in 
  such 
  regions 
  plants 
  often 
  grow 
  upon 
  one 
  another 
  in 
  quantities 
  

   that 
  break 
  down 
  the 
  supporting 
  stems 
  

  

  domesticated 
  plants 
  have 
  been 
  derived 
  from 
  wild 
  ancestors. 
  

   Many 
  of 
  these 
  have 
  been 
  improved, 
  until 
  now 
  their 
  prod- 
  

   ucts 
  are 
  of 
  much 
  better 
  quality 
  or 
  quantity 
  than 
  in 
  their 
  wild 
  

  

  