﻿10 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  and 
  terminal 
  rootlets 
  have 
  no 
  bark, 
  and 
  from 
  their 
  surfaces 
  

   tin-re 
  grow 
  very 
  fine 
  tubular 
  threads 
  known 
  us 
  root 
  luiirs 
  

   ( 
  tigs. 
  :. 
  and 
  ' 
  ). 
  Root 
  hairs 
  have 
  extremely 
  thin 
  walls, 
  through 
  

   \vlueh 
  water 
  from 
  the 
  soil 
  can 
  pass 
  into 
  the 
  interior; 
  thence 
  it 
  

   passes 
  upward 
  through 
  rootlets 
  and 
  larger 
  roots, 
  through 
  the 
  

   stem 
  and 
  into 
  the 
  leaves. 
  Substances 
  that 
  are 
  in 
  solution 
  in 
  

   the 
  soil 
  water 
  may 
  be 
  transferred 
  into 
  the 
  plant 
  through 
  the 
  

  

  delicate 
  walls 
  of 
  the 
  root 
  hairs 
  and 
  

   their 
  lining. 
  Root 
  hairs 
  do 
  not 
  

   grow 
  over 
  all 
  the 
  surface 
  of 
  the 
  

   terminal 
  rootlets, 
  but 
  develop 
  a 
  

   little 
  way 
  from 
  the 
  root 
  tip. 
  They 
  

   do 
  not 
  live 
  very 
  long, 
  the 
  older 
  

   ones 
  constantly 
  dying. 
  Tims, 
  as 
  

   the 
  root 
  tip 
  grows 
  forward 
  through 
  

   the 
  soil 
  the 
  actual 
  number 
  of 
  root 
  

   hairs 
  on 
  a 
  rootlet 
  may 
  remain 
  prac- 
  

   tically 
  constant 
  during 
  the 
  growing 
  

   season, 
  on 
  account 
  of 
  the 
  dying 
  of 
  

   older 
  root 
  hairs 
  and 
  the 
  develop- 
  

   ment 
  of 
  new 
  ones 
  near 
  the 
  root 
  tip 
  

   on 
  the 
  new 
  growth 
  of 
  the 
  rootlet. 
  

   It 
  is 
  evident 
  that 
  the 
  area 
  of 
  root 
  

   hairs 
  advances, 
  although 
  no 
  indi- 
  

   vidual 
  root 
  hairs 
  move 
  forward 
  

   through 
  the 
  soil. 
  Although 
  ex- 
  

   tremely 
  delicate 
  in 
  structure, 
  root 
  

   hairs 
  grow 
  between 
  and 
  around 
  the 
  hard 
  particles 
  of 
  soil 
  

   < 
  tig. 
  ('). 
  It 
  is 
  easy 
  to 
  count 
  the 
  root 
  hairs 
  on 
  a 
  small 
  portion 
  

   of 
  the 
  root. 
  Corn 
  rootlets 
  grown 
  in 
  damp 
  air 
  have 
  been 
  found 
  

   to 
  hear 
  l_~> 
  root 
  hairs 
  on 
  an 
  area 
  ^ 
  inch 
  square. 
  The 
  large 
  

   number 
  of 
  rootlets 
  and 
  the 
  enormous 
  number 
  of 
  root 
  hairs 
  

   serve 
  to 
  make 
  a 
  network 
  which 
  completely 
  permeates 
  the 
  soil 
  

   in 
  the 
  region 
  of 
  the 
  rootlets. 
  The 
  root 
  hairs 
  are 
  the 
  chief 
  

   organs 
  by 
  which 
  water 
  and 
  substances 
  in 
  solution 
  in 
  water; 
  

   are 
  absorbed 
  from 
  the 
  soil. 
  

  

  FH;. 
  '). 
  A 
  mustard 
  sivdlini,' 
  

  

  tin 
  ) 
  \v 
  n 
  in 
  a 
  hand 
  of 
  tiller 
  papfr 
  

  

  in.-idi- 
  a 
  drinkiim 
  iclass. 
  BO 
  as 
  to 
  

  

  sliu\v 
  the 
  root 
  hairs 
  

  

  Note 
  the 
  difference 
  in 
  length 
  and 
  

  

  condition 
  of 
  tin- 
  root 
  hairs 
  on 
  Ilic 
  

  

  different 
  parts 
  of 
  the 
  root 
  

  

  