﻿64 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  1. 
  The 
  epidermis 
  (ep.) 
  serves 
  as 
  a 
  protective 
  covering 
  for 
  

   the 
  young 
  stem 
  and, 
  to 
  a 
  considerable 
  extent, 
  prevents 
  it 
  from 
  

   becoming 
  dried 
  up. 
  

  

  2. 
  The 
  layers 
  of 
  cork 
  cells 
  soon 
  formed 
  just 
  beneath 
  the 
  

   epidermis 
  (not 
  separately 
  shown 
  in 
  the 
  diagram) 
  prevent 
  loss 
  

   of 
  water 
  and 
  consequent 
  drying 
  up. 
  

  

  3. 
  The 
  layers 
  of 
  green 
  cells 
  which 
  at 
  first 
  

   directly 
  underlie 
  the 
  epidermis 
  (not 
  distinguish- 
  

   able 
  in 
  the 
  diagram) 
  are 
  useful 
  in 
  the 
  manu- 
  

   facture 
  of 
  plant 
  food. 
  1 
  

  

  4. 
  The 
  fibrous 
  cells 
  of 
  the 
  hard 
  bast 
  give 
  

   touglmess 
  to 
  the 
  stem. 
  

  

  5. 
  Certain 
  thin-walled 
  e 
  

   tubes 
  (si) 
  of 
  the 
  outer 
  

   portions 
  of 
  the 
  bun- 
  c 
  

   dies 
  carry 
  manufactured 
  

   plant 
  food 
  in 
  liquid 
  form 
  

   downward, 
  or 
  toward 
  

   the 
  roots. 
  

  

  6. 
  The 
  cambium 
  layer 
  

   (in 
  figure 
  42, 
  A 
  shown 
  

   proportionally 
  thicker 
  

   than 
  it 
  really 
  is) 
  gro\\ 
  s 
  

   and 
  forms 
  new 
  bark 
  on 
  

   its 
  outer 
  side, 
  while 
  on 
  

   its 
  inner 
  side 
  it 
  forms 
  

   new 
  wood 
  ( 
  see 
  sect. 
  > 
  1 
  ). 
  

  

  7. 
  The 
  vessels, 
  or 
  

  

  ducts 
  (?>), 
  of 
  tin- 
  l)in 
  idles 
  cany 
  water 
  upward, 
  or 
  toward 
  the 
  

   leaves. 
  The 
  libers, 
  which 
  constitute 
  a 
  considerable 
  portion 
  of 
  

   the 
  wood 
  part 
  of 
  the 
  bundles, 
  stit'ten 
  the 
  stem 
  and 
  make 
  it 
  

   tougher. 
  

  

  61. 
  Strengthening 
  cells. 
  The 
  cells 
  which 
  serve 
  to 
  stiffen 
  or 
  

   toughen 
  the 
  roots, 
  stems, 
  and 
  leaves 
  of 
  plants 
  belong 
  to 
  sev- 
  

   eral 
  different 
  types. 
  The 
  two 
  kinds 
  shown 
  in 
  figure 
  44 
  are 
  

  

  1 
  See 
  section 
  60. 
  

  

  A 
  1> 
  

  

  Kic. 
  44. 
  A, 
  strengthening 
  and 
  other 
  tissue 
  

  

  from 
  stem 
  of 
  balsam 
  (Imjinfii 
  nn)\ 
  B, 
  a 
  group 
  

  

  of 
  hard-bast 
  fibers 
  

  

  e, 
  epidermis; 
  c, 
  coilenchyma 
  ; 
  /, 
  intercellular 
  

  

  spaces 
  liet\\eell 
  la 
  l'L;e 
  parenchyma 
  cells 
  ; 
  il, 
  Cllt- 
  

  

  olT 
  ends 
  : 
  l>. 
  lengthwise 
  section 
  of 
  tiliers. 
  < 
  i 
  really 
  

   ma-nitied. 
  .1, 
  after 
  Strashiirucr 
  ; 
  /,'. 
  afterTsi-liiivh 
  

  

  