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SUMMARY. 
Plant  improvement  is  based  on  the  principles  of  evolution. 
In  order  to  obtain  the  best  results  with  the  expenditure  of  the 
least  energy,  good  judgment  and  a high  degree  of  training  is 
required.  The  plant  is  the  result  of  heredity  and  environment. 
Three  steps  in  improving  plants : 
1 To  find  or  induce  variation: 
(1)  By  change  of  environment: 
(a)  food  supply, 
(b)  soil, 
(c)  climate, 
(d)  space, 
(e)  cultivation. 
(2)  By  crossing : 
(a)  to  combine  good  qualities, 
(b)  to  create  new  varieties  or  strains. 
2 Selection : 
(1)  Best  characters; 
(2)  Corelated  characters. 
3 Testing  and  propagation. 
FOREST  RESOURCES  OF  SOUTH  AMERICA. 
The  forests  of  South  America  are  principally  tropical,  but  in 
the  Andes  Mountains  and  the  southern  end  of  the  continent  are 
found  forests  of  a temperate  and  sub-arctic  character  resembling 
somewhat  those  of  the  United  States  and  Canada. 
The  tropical  forests  are  totally  different  from  our  north  woods. 
There  are  no  solid  stands  of  single  species  or  even  of  a few 
mixed  species.  Instead,  hundreds  of  kinds  of  trees  grow  thor- 
oughly mixed  and  scattered  through  the  whole  forest.  This  is 
one  of  several  reasons  that  makes  logging  in  tropical  forests  so 
expensive  and  often  unprofitable. 
Rubber  hunters  have  explored  nearly  the  whole  tropical  forest 
in  search  of  that  necessary  article  of  commerce,  but  aside  from 
that  South  American  forests  have  only  been  cut  into  for  a few 
miles  back  from  the  coast  and  the  principal  ports  and  rivers. 
Even  in  this  area  only  the  species  at  present  most  valuable  for 
commerce  have  been  thus  far  cut,  for  example,  cedar,  mahogany, 
rosewood,  lignum-vitae,  fustic  and  ironwood.  Railroads,  where 
they  exist,  charge  such  exorbitant  freight  rates  that  they  have 
not  much  encouraged  exploitation  of  the  forests. 
