﻿THE 
  STEM 
  AND 
  THE 
  LEAF 
  

  

  69 
  

  

  which 
  active 
  cambium 
  remains, 
  are 
  said 
  to 
  be 
  open. 
  The 
  

   palms 
  and 
  similar 
  monocotyledonous 
  trees 
  cannot 
  form 
  an- 
  

   nual 
  rings 
  of 
  wood. 
  There 
  are, 
  however, 
  

   sti 
  a 
  few 
  tree-like 
  monocotyledons 
  in 
  which 
  

  

  the 
  trunk 
  continues 
  for 
  years 
  to 
  increase 
  

   in 
  thickness, 
  and 
  may 
  reach 
  great 
  dimen- 
  

   sions, 
  but 
  these 
  trunks 
  do 
  not 
  thicken 
  

   in 
  the 
  same 
  way 
  as 
  do 
  the 
  trunks 
  of 
  our 
  

   familiar 
  trees. 
  

  

  Many 
  of 
  the 
  woody 
  monocotyledons 
  are 
  

   remarkable 
  for 
  the 
  extraordinary 
  length 
  

   and 
  slenderness 
  of 
  their 
  stems. 
  The 
  rat- 
  

   tans, 
  for 
  example, 
  often 
  climb 
  for 
  hun- 
  

   dreds 
  of 
  feet 
  among 
  the 
  tops 
  of 
  tropical 
  

   forest 
  trees. 
  

  

  68. 
  The 
  parts 
  of 
  the 
  leaf. 
  It 
  already 
  

  

  has 
  been 
  stated 
  in 
  section 
  11 
  that 
  a 
  leaf 
  

   FIG. 
  48. 
  A 
  young 
  leaf 
  cons 
  i 
  sts 
  o 
  f 
  pet 
  . 
  

  

  of 
  wild 
  black 
  cherry 
  . 
  , 
  

  

  iole 
  and 
  blade. 
  

   bl, 
  blade, 
  or 
  expanded 
  

  

  part; 
  sta, 
  leaf 
  stalk 
  ; 
  sti, 
  A 
  tew 
  WOl'ds 
  

   stipules, 
  or 
  appendages 
  at 
  mav 
  now 
  b 
  e 
  sa 
  i 
  c 
  ] 
  

   the 
  base 
  of 
  the 
  leafstalk 
  J 
  

  

  about 
  the 
  exter- 
  

   nal 
  forms 
  of 
  ordinary 
  leaves 
  and 
  the 
  

   parts 
  of 
  which 
  they 
  consist. 
  

  

  At 
  the 
  base 
  of 
  the 
  petiole 
  many 
  

   leaves 
  bear 
  a 
  pair 
  of 
  appendages 
  

   called 
  stipules 
  (figs. 
  48 
  and 
  49). 
  In 
  

   some 
  leaves, 
  as 
  those 
  of 
  the 
  pansy, 
  

   these 
  form 
  an 
  important 
  part 
  of 
  the 
  FIG. 
  49. 
  Tip 
  of 
  a 
  geranium 
  

   total 
  leaf 
  surface. 
  Not 
  infrequently, 
  (Pelargonium) 
  shoot 
  

  

  as 
  in 
  the 
  black 
  locust, 
  the 
  stipules 
  bl 
  t 
  > 
  blade 
  { 
  a 
  f 
  leaf 
  / 
  "' 
  blade 
  

  

  of 
  a 
  young 
  leaf, 
  only 
  partly 
  ex- 
  

   have 
  the 
  form 
  of 
  thorns, 
  One 
  at 
  each 
  panded 
  from 
  the 
  naked 
  bud 
  ; 
  

  

  side 
  of 
  the 
  base 
  of 
  the 
  petiole. 
  l 
  < 
  leafstalk; 
  * 
  stipules. 
  Con- 
  

  

  Biderably 
  reduced 
  

   In 
  general 
  the 
  form 
  of 
  the 
  leaf 
  

  

  depends 
  very 
  much 
  on 
  the 
  distribution 
  of 
  the 
  groups 
  of 
  fibro- 
  

   vascular 
  bundles 
  known 
  as 
  veins. 
  Most 
  monocotyledons 
  have 
  

  

  8t 
  

  

  