﻿48 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  conditions 
  under 
  which 
  plants 
  produce 
  most 
  abundantly. 
  They 
  

   must 
  study 
  and 
  improve 
  those 
  plants 
  which 
  are 
  found 
  to 
  

   perform 
  their 
  nutritive 
  functions 
  in 
  such 
  a 
  way 
  that 
  large 
  

   amounts 
  of 
  dr>iral>le 
  food 
  are 
  produced 
  economically. 
  

  

  The 
  island 
  of 
  Chung-ming, 
  at 
  the 
  mouth 
  of 
  the 
  Yangtze 
  

   Uiver 
  in 
  China, 
  has 
  ;ui 
  area 
  of 
  270 
  square 
  miles. 
  It 
  has 
  but 
  one 
  

   large 
  city, 
  yet 
  the 
  whole 
  island 
  has 
  a 
  dense 
  population. 
  The 
  

   inhabitants 
  have 
  made 
  such 
  a 
  study 
  of 
  the 
  productivity 
  of 
  

   plants 
  that 
  the 
  island 
  is 
  said 
  to 
  support 
  a 
  population 
  of 
  3700 
  

   people 
  per 
  square 
  mile. 
  Our 
  own 
  rural 
  population 
  of 
  61 
  per 
  

   square 
  mile 
  of 
  improved 
  land 
  suggests 
  by 
  comparison 
  the 
  

   necessity 
  of 
  further 
  study 
  of 
  the 
  food 
  cycle 
  of 
  plants 
  and 
  of 
  

   the 
  conditions 
  under 
  which 
  our 
  economic 
  plants 
  thrive 
  best. 
  

  

  48. 
  Independent 
  and 
  dependent 
  plants. 
  So 
  far 
  in 
  this 
  chapter 
  

   we 
  have 
  spoken 
  only 
  of 
  plants 
  that 
  have 
  chlorophyll 
  and 
  can 
  

   make 
  their 
  own 
  food 
  from 
  materials 
  that 
  are 
  not 
  ordinarily 
  

   regarded 
  as 
  nutrient 
  substances 
  ; 
  that 
  is, 
  we 
  have 
  discussed 
  

   only 
  independent 
  plants. 
  But 
  there 
  are 
  many 
  plants 
  that 
  do 
  

   not 
  possess 
  chlorophyll, 
  and 
  even 
  some 
  that 
  do 
  possess 
  it, 
  that 
  

   are 
  dependent 
  for 
  their 
  food 
  upon 
  the 
  chlorophyll 
  work 
  of 
  

   plants 
  similar 
  to 
  those 
  we 
  have 
  already 
  discussed. 
  Then 
  some 
  

   plants 
  are 
  dependent, 
  not 
  for 
  food, 
  but 
  in 
  other 
  ways. 
  Some 
  

   dependent 
  flowering 
  plants, 
  like 
  the 
  woodbine, 
  or 
  Virginia 
  

   creeper, 
  are 
  almost 
  independent. 
  A 
  woodbine 
  may 
  grow 
  in 
  

   the 
  open 
  and 
  attain 
  its 
  full 
  size, 
  but 
  in 
  dense 
  woodlands 
  

   grapevines, 
  woodbines, 
  and 
  many 
  other 
  climbers 
  can 
  only 
  

   make 
  a 
  normal 
  growth 
  by 
  climbing 
  upon 
  the 
  trunks 
  of 
  trees 
  

   and 
  so 
  raising 
  themselves 
  into 
  the 
  light. 
  

  

  49. 
  The 
  food 
  supply 
  and 
  dependency 
  in 
  flowering 
  plants. 
  1 
  

   The 
  principal 
  groups 
  into 
  which 
  dependent 
  flowering 
  plants 
  

   are 
  divided 
  are 
  as 
  follows 
  : 
  

  

  1. 
  Lianas, 
  or 
  climbers. 
  

  

  2. 
  Epiphytes, 
  or 
  plants 
  which 
  rest 
  upon 
  other 
  plants. 
  

  

  3. 
  Saprophytes, 
  or 
  plants 
  which 
  live 
  on 
  the 
  products 
  of 
  the 
  

   decay 
  of 
  organic 
  matter. 
  

  

  1 
  Dependency 
  among 
  lower 
  plants 
  is 
  discussed 
  at 
  length 
  in 
  later 
  chapters. 
  

  

  