﻿46 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  and 
  consume 
  part 
  or 
  all 
  of 
  it 
  in 
  the 
  growth 
  of 
  the 
  following 
  

   spring. 
  Trees 
  and 
  shrubs 
  in 
  temperate 
  or 
  cold 
  climates 
  store 
  

   starch 
  and 
  other 
  foods 
  in 
  the 
  roots, 
  as 
  well 
  as 
  in 
  the 
  stem. 
  

   It 
  is 
  the 
  stored 
  food 
  in 
  the 
  root 
  that 
  enables 
  such 
  plants 
  as 
  

   rhubarb, 
  the 
  peony, 
  some 
  buttercups, 
  sweet 
  cicely, 
  the 
  dande- 
  

   lion, 
  and 
  many 
  others 
  to 
  make 
  a 
  quick 
  growth 
  in 
  the 
  spring, 
  

   before 
  the 
  weather 
  is 
  warm 
  enough 
  for 
  the 
  manufacture 
  of 
  

   much 
  plant 
  food. 
  The 
  starch, 
  sugar, 
  and 
  proteins 
  which 
  

   abound 
  in 
  many 
  roots 
  or 
  root-like 
  portions 
  of 
  plants 
  make 
  

   them 
  valuable 
  for 
  food, 
  as 
  in 
  the 
  case 
  of 
  beets, 
  turnips, 
  car- 
  

   rots, 
  parsnips, 
  sweet 
  potatoes, 
  salsify, 
  and 
  the 
  cassava 
  plant, 
  

   from 
  which 
  tapioca 
  is 
  made. 
  

  

  45. 
  Digestion 
  and 
  assimilation. 
  Plants 
  as 
  well 
  as 
  animals 
  

   must 
  make 
  solid 
  foods 
  into 
  solutions 
  before 
  these 
  foods 
  can 
  

   become 
  parts 
  of 
  the 
  living 
  protoplasm. 
  The 
  processes 
  which 
  

   make 
  these 
  solids 
  into 
  solutions 
  are 
  known 
  by 
  the 
  general 
  

   name 
  of 
  digestion. 
  Digestive 
  processes 
  vary 
  widely 
  in 
  different 
  

   jiving 
  tilings. 
  Animals 
  usually 
  have 
  special 
  organs 
  for 
  this 
  

   work, 
  but 
  plants 
  do 
  not 
  have 
  them. 
  The 
  process 
  is 
  essentially 
  

   the 
  same 
  in 
  both, 
  however, 
  though 
  it 
  may 
  be 
  much 
  more 
  com- 
  

   plex 
  in 
  some 
  higher 
  animals 
  than 
  in 
  plants. 
  Plants 
  form 
  cer- 
  

   tain 
  chemical 
  substances 
  known 
  as 
  enzymes 
  (see 
  sect. 
  157). 
  

   which 
  operate 
  in 
  ways 
  that 
  are 
  little 
  understood, 
  but 
  which 
  

   result 
  in 
  digesting 
  foods. 
  

  

  By 
  a 
  process 
  known 
  as 
  axx!>nil<iti<>n 
  digested 
  foods 
  may 
  be 
  

   taken 
  into 
  living 
  protoplasm 
  and 
  made 
  a 
  part 
  of 
  it, 
  What 
  

   occurs 
  in 
  assimilation 
  no 
  one 
  really 
  knows. 
  Digested 
  food 
  

   becomes 
  living 
  protoplasm, 
  ami 
  in 
  so 
  doing 
  it 
  becomes 
  more 
  

   complex 
  in 
  structure. 
  Thus 
  far 
  it 
  has 
  been 
  impossible 
  for 
  

   scientists 
  to 
  follow 
  the 
  process 
  closely 
  enough 
  to 
  determine 
  

   the 
  changes 
  which 
  assimilation 
  makes, 
  though 
  it 
  is 
  known 
  

   that 
  living 
  substance 
  is 
  the 
  outcome. 
  

  

  46. 
  Respiration. 
  Food 
  that 
  has 
  been 
  digested 
  and 
  assimi- 
  

   lated, 
  thus 
  becoming 
  living 
  tissue, 
  is 
  later 
  changed 
  by 
  the 
  

   process 
  known 
  as 
  fcxfiiratinn. 
  It 
  is 
  common 
  to 
  associate 
  

   respiration, 
  in 
  both 
  plants 
  and 
  animals, 
  with 
  the 
  interchange 
  of 
  

  

  