﻿4 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  condition. 
  In 
  the 
  case 
  of 
  some 
  of 
  these 
  domesticated 
  plants 
  

   -for 
  example, 
  wheat- 
  it 
  is 
  possible 
  that 
  a 
  single 
  wild 
  plant 
  

   may 
  have 
  produced 
  as 
  much 
  and 
  as 
  g 
  1 
  wheat 
  as 
  one 
  cul- 
  

   tivated 
  plant 
  does 
  now, 
  but 
  in 
  most 
  < 
  -ases, 
  doubtless, 
  great 
  

   improvements 
  have 
  been 
  made, 
  and 
  in 
  all 
  cases 
  the 
  total 
  

   product 
  has 
  been 
  vastly 
  increased. 
  The 
  northwestern 
  United 
  

   States 
  produces 
  wheat 
  that 
  is 
  of 
  great 
  importance 
  to 
  the 
  wel- 
  

   fare 
  of 
  the 
  nation. 
  In 
  the 
  corn 
  belt 
  of 
  the 
  central 
  United 
  

   States 
  there 
  are 
  seven 
  states 
  that 
  produce 
  nearly 
  half 
  the 
  

   corn 
  used 
  in 
  the 
  whole 
  world 
  --an 
  amount 
  that 
  is 
  ordinarily 
  

   \\orth 
  annually 
  almost 
  three 
  billion 
  dollars. 
  The 
  cotton 
  crop 
  

   of 
  the 
  Southern 
  states 
  (three 
  fifths 
  of 
  the 
  cotton 
  of 
  the 
  world), 
  

   together 
  with 
  cotton-seed 
  products, 
  is 
  worth 
  annually 
  nearly 
  

   one 
  billion 
  dollars. 
  

  

  3. 
  Plants 
  are 
  everywhere. 
  Cultivated 
  plants 
  constitute 
  only 
  

   a 
  very 
  small 
  part 
  of 
  the 
  plant 
  population 
  of 
  the 
  earth. 
  In 
  fact, 
  

   we 
  are 
  so 
  accustomed 
  to 
  seeing 
  plant 
  life 
  on 
  every 
  hand 
  that 
  

   we 
  ordinarily 
  think 
  little 
  about 
  it. 
  Most 
  people 
  have 
  never 
  

   been 
  in 
  surroundings 
  where 
  plant 
  life 
  is 
  not 
  fairly 
  abundant. 
  

   The 
  upper 
  parts 
  of 
  the 
  cones 
  of 
  active 
  volcanoes 
  and 
  the 
  in- 
  

   teriors 
  of 
  their 
  craters, 
  a 
  few 
  mud 
  volcanoes 
  and 
  hot 
  springs, 
  

   the 
  exposed 
  surfaces 
  of 
  arctic 
  ice 
  fields 
  or 
  of 
  glaciers, 
  together 
  

   with 
  a 
  few 
  poisonous 
  alkali 
  tracts, 
  are 
  almost 
  the 
  only 
  parts 
  

   of 
  the 
  earth's 
  surface 
  on 
  which 
  or 
  in 
  which 
  plant 
  life 
  is 
  

   not 
  present. 
  There 
  are, 
  however, 
  very 
  great 
  differences 
  in 
  the 
  

   density 
  of 
  the 
  plant 
  population 
  of 
  different 
  regions. 
  Many 
  

   deserts 
  have 
  only 
  here 
  and 
  there 
  a 
  shrub 
  or 
  other 
  plant 
  capa- 
  

   ble 
  of 
  enduring 
  the 
  inhospitable 
  soil 
  and 
  climatic 
  conditions 
  

   there 
  encountered. 
  In 
  the 
  sand 
  hills 
  which 
  are 
  found 
  along 
  

   the 
  Great 
  Lakes 
  ( 
  iig. 
  1), 
  along 
  the 
  shores 
  of 
  the 
  Atlantic 
  

   Ocean, 
  and 
  else\\ 
  here 
  few 
  plants 
  are 
  able 
  to 
  grow. 
  On 
  the 
  

   other 
  hand, 
  a 
  weedy 
  garden, 
  a 
  grass 
  lawn, 
  or 
  a 
  meadow 
  usually 
  

   has 
  hundreds 
  of 
  plants 
  to 
  every 
  square 
  yard 
  of 
  surface, 
  and 
  

   tropical 
  forests 
  often 
  present 
  a 
  tan-led 
  mass 
  of 
  vegetation 
  

   (ti-. 
  -) 
  towering 
  up 
  to 
  a 
  height 
  of 
  nearly 
  two 
  hundred 
  feet, 
  

   interlaced 
  with 
  climbing 
  plants, 
  sometimes 
  hundreds 
  of 
  feet 
  

  

  