﻿44 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  if 
  tested 
  with 
  iodine 
  for 
  starch. 
  During 
  the 
  winter 
  imu-h 
  of 
  

   this 
  starch 
  is 
  often 
  converted 
  into 
  sugar 
  or 
  oil. 
  The 
  presence 
  of 
  

   proteins 
  in 
  wood 
  is 
  so 
  general 
  that 
  the 
  cheaper 
  grades 
  of 
  white 
  

   paper, 
  largely 
  made 
  of 
  wood 
  pulp, 
  at 
  once 
  turn 
  yellow 
  on 
  being 
  

   moistened 
  with 
  nitric 
  acid 
  (the 
  protein 
  test). 
  When 
  thus 
  tested, 
  

   paper 
  made 
  wholly 
  of 
  cotton 
  or 
  of 
  linen 
  rags 
  shows 
  little 
  change. 
  

   The 
  plant 
  food 
  stored 
  in 
  wood 
  is 
  most 
  abundant 
  in 
  the 
  younger 
  

   portions 
  (sapwood) 
  and 
  above 
  all 
  in 
  the 
  cambium 
  layer. 
  

  

  Underground 
  stems 
  and 
  roots 
  (fig. 
  30) 
  often 
  contain 
  large 
  

   quantities 
  of 
  stored 
  food 
  and 
  are 
  thus 
  useful 
  in 
  tiding 
  the 
  

   plant 
  ovar 
  that 
  period 
  of 
  the 
  year 
  when 
  no 
  food 
  can 
  be 
  made. 
  

   In 
  the 
  same 
  way 
  they 
  are 
  of 
  service 
  in 
  storing 
  water, 
  as 
  has 
  

   already 
  been 
  shown 
  (sect. 
  21). 
  There 
  are 
  many 
  shade 
  plants, 
  

   such 
  as 
  trilliums, 
  dogtooth 
  violets, 
  wild 
  ginger, 
  May 
  apple, 
  

   and 
  others, 
  which 
  leaf 
  and 
  flower 
  early 
  in 
  the 
  spring 
  and 
  do 
  

   a 
  large 
  part 
  of 
  the 
  storing 
  of 
  food 
  for 
  the 
  next 
  season 
  in 
  their 
  

   rootstocks, 
  tubers, 
  or 
  bulbs, 
  before 
  the 
  trees 
  under 
  which 
  they 
  

   grow 
  are 
  in 
  such 
  full 
  leaf 
  as 
  to 
  shut 
  out 
  the 
  abundant 
  light 
  

   necessary 
  for 
  photosynthesis. 
  

  

  Fleshy 
  leaves 
  often 
  contain 
  much 
  stored 
  food, 
  as 
  in 
  the 
  famil- 
  

   iar 
  century 
  plant, 
  which, 
  after 
  storing 
  food 
  for 
  fifteen 
  years 
  01 
  

   more, 
  may 
  use 
  this 
  food 
  in 
  producing 
  an 
  immense 
  flowering 
  

   stalk 
  and 
  many 
  flowers 
  and 
  seeds. 
  By 
  the 
  end 
  of 
  the 
  flowering 
  

   season 
  the 
  leaves, 
  in 
  the 
  case 
  of 
  century 
  plants 
  that 
  were 
  tested, 
  

   had 
  lost 
  more 
  than 
  90 
  per 
  cent 
  of 
  their 
  weight. 
  This 
  flowering 
  

   stalk 
  may 
  reach 
  a 
  height 
  of 
  over 
  33 
  feet 
  and 
  a 
  weight 
  of 
  some 
  

   500 
  pounds. 
  Its 
  average 
  growth 
  in 
  height, 
  during 
  the 
  month 
  

   of 
  most 
  rapid 
  elongation 
  has 
  been 
  found 
  to 
  be 
  about 
  5^ 
  inches 
  

   a 
  day. 
  Not 
  only 
  the 
  plant 
  food 
  but 
  also 
  nearly 
  all 
  the 
  water 
  

   for 
  this 
  rapid 
  growth 
  is 
  furnished 
  by 
  the 
  leaves. 
  

  

  44. 
  Relation 
  of 
  food 
  and 
  water 
  storage 
  to 
  duration 
  of 
  life. 
  

   It 
  is 
  usual 
  to 
  divide 
  plants, 
  according 
  to 
  their 
  duration 
  of 
  life, 
  

   into 
  three 
  classes: 
  OHI/IKI/*, 
  those 
  living 
  one 
  year 
  or 
  less; 
  lirtt- 
  

   niah, 
  those 
  living 
  two 
  years 
  ; 
  perennials, 
  those 
  living 
  more 
  

   than 
  two 
  years. 
  The 
  boundaries 
  between 
  these 
  classes 
  are 
  

   not 
  always 
  definite. 
  For 
  example, 
  winter 
  wheat 
  is 
  an 
  annual, 
  

  

  