﻿PLANT 
  INDUSTRIES 
  309 
  

  

  about 
  the 
  growth 
  of 
  plants. 
  This 
  requires 
  a 
  knowledge 
  of 
  the 
  

   facts 
  that 
  are 
  known 
  about 
  the 
  structure 
  of 
  plants, 
  the 
  con- 
  

   ditions 
  of 
  soil, 
  temperature, 
  moisture, 
  etc. 
  under 
  which 
  they 
  

   thrive 
  best, 
  the 
  nature 
  of 
  plant 
  and 
  animal 
  diseases 
  and 
  the 
  

   means 
  of 
  preventing 
  them, 
  and 
  the 
  best 
  methods 
  of 
  utilizing 
  

   plant 
  products 
  after 
  the 
  plant 
  has 
  made 
  them. 
  Second, 
  the 
  life 
  

   of 
  a 
  plant, 
  like 
  that 
  of 
  an 
  animal, 
  is 
  a 
  very 
  intricate 
  matter, 
  and 
  

   there 
  are 
  many 
  highly 
  important 
  questions 
  upon 
  which 
  science 
  

   as 
  yet 
  has 
  little 
  positive 
  knowledge. 
  Each 
  plan 
  t 
  industry, 
  there- 
  

   fore, 
  involves 
  many 
  unsolved 
  problems, 
  about 
  which 
  we 
  need 
  

   to 
  secure 
  additional 
  knowledge. 
  Thus, 
  science 
  has 
  discovered 
  

   what 
  kind 
  of 
  cultivation 
  will 
  best 
  enable 
  the 
  corn 
  plant 
  to 
  

   thrive; 
  but, 
  although 
  botanists 
  know 
  the 
  life 
  cycle 
  of 
  the 
  

   smut 
  which 
  attacks 
  corn, 
  a 
  practical 
  and 
  thoroughly 
  effective 
  

   way 
  of 
  preventing 
  the 
  attack 
  has 
  not 
  yet 
  been 
  found. 
  

  

  294. 
  The 
  sugar 
  industry. 
  Nearly 
  all 
  plants 
  that 
  do 
  the 
  work 
  

   of 
  photosynthesis 
  produce 
  sugar 
  of 
  some 
  kind. 
  In 
  some 
  plants 
  

   the 
  amount 
  produced 
  may 
  be 
  extremely 
  small, 
  and 
  it 
  may 
  re- 
  

   main 
  as 
  sugar 
  only 
  for 
  a 
  brief 
  period 
  before 
  it 
  is 
  made 
  into 
  

   some 
  other 
  compound 
  and 
  assimilated 
  into 
  living 
  substance 
  or 
  

   stored 
  within 
  the 
  plant. 
  In 
  other 
  plants 
  the 
  amount 
  may 
  be 
  

   large, 
  and 
  may 
  be 
  retained 
  as 
  sugar 
  for 
  long 
  periods. 
  It 
  may 
  

   be 
  stored 
  as 
  sugar 
  or, 
  more 
  often, 
  as 
  starch, 
  which 
  is 
  usually 
  

   changed 
  to 
  sugar 
  again 
  for 
  transference 
  through 
  the 
  plant. 
  

   Plants 
  of 
  the 
  latter 
  class 
  may 
  prove 
  useful 
  in 
  the 
  sugar 
  in- 
  

   dustries. 
  It 
  is 
  possible 
  that 
  wild 
  plants 
  may 
  yet 
  be 
  found 
  

   that 
  are 
  valuable 
  for 
  this 
  sugar 
  content, 
  but 
  at 
  present 
  a 
  few 
  

   species 
  produce 
  the 
  sugar 
  of 
  the 
  world. 
  The 
  sugar 
  maple 
  

   (Acer 
  saccharum) 
  (fig. 
  233) 
  has 
  long 
  been 
  used 
  as 
  a 
  source 
  

   of 
  sugar. 
  Other 
  species 
  of 
  the 
  same 
  genus 
  produce 
  sweet 
  

   sap, 
  but 
  not 
  so 
  abundantly 
  as 
  the 
  sugar 
  maple. 
  The 
  tree 
  

   belongs 
  to 
  the 
  type 
  of 
  primeval 
  forest 
  that 
  prevailed 
  in 
  the 
  

   north-central 
  and 
  northeastern 
  parts 
  of 
  North 
  America. 
  In 
  

   early 
  spring 
  the 
  previous 
  season's 
  surplus 
  of 
  sugar 
  is 
  trans- 
  

   ported 
  to 
  the 
  parts 
  of 
  the 
  tree 
  where, 
  a 
  little 
  later, 
  there 
  is 
  

   active 
  growth 
  of 
  new 
  leaves. 
  This 
  stored 
  sugar 
  is 
  used 
  in 
  

  

  