﻿T. 
  Holm 
  — 
  Studies 
  in 
  the 
  Cyperacece. 
  123 
  

  

  transverse 
  section 
  of 
  one 
  of 
  these 
  scale-like 
  leaves 
  shows 
  us 
  a 
  

   structure, 
  which 
  in 
  most 
  respects 
  reminds 
  us 
  of 
  a 
  leaf-sheath, 
  

   viz 
  : 
  the 
  development 
  of 
  large 
  lacunes 
  between 
  the 
  mestome- 
  

   bundles, 
  the 
  non-differentiation 
  of 
  the 
  mesophyll 
  and 
  the 
  par- 
  

   tial 
  absence 
  of 
  vessels 
  in 
  the 
  mestome-bundles, 
  while 
  the 
  

   leptome-elements 
  are 
  well-developed. 
  The 
  stereome 
  is, 
  also, 
  

   characteristic, 
  forming 
  large 
  groups 
  on 
  the 
  dorsal 
  face 
  of 
  the 
  

   leaf 
  underneath 
  the 
  leptome-side 
  of 
  the 
  mestome-bundles 
  ; 
  

   besides 
  it, 
  also, 
  forms 
  isolated 
  groups 
  between 
  the 
  bundles. 
  

   The 
  corresponding 
  groups 
  of 
  stereome 
  on 
  the 
  ventral 
  face 
  are 
  

   smaller, 
  and 
  the 
  cell-walls 
  are 
  relatively 
  thin, 
  leaving 
  a 
  large 
  

   lumen. 
  The 
  free 
  part 
  of 
  the 
  scale-like 
  leaf 
  shows 
  a 
  similar 
  

   structure, 
  and 
  the 
  free 
  margins 
  consist 
  only 
  of 
  two 
  strata 
  of 
  

   cells, 
  corresponding 
  to 
  the 
  dorsal 
  and 
  ventral 
  epidermis. 
  

  

  The 
  large, 
  green 
  leaf 
  has 
  a 
  similarly 
  developed 
  epidermis 
  on 
  

   both 
  faces, 
  but 
  stomata 
  are 
  present 
  in 
  large 
  number 
  on 
  both 
  

   faces, 
  but 
  most 
  numerous 
  on 
  the 
  inferior, 
  the 
  dorsal 
  face. 
  

   These 
  stomata 
  show 
  the 
  same, 
  characteristic 
  form 
  as 
  recorded 
  

   by 
  Schwendener 
  (1. 
  c), 
  but 
  they 
  are 
  constantly 
  in 
  niveau 
  with 
  

   the 
  surrounding 
  epidermis 
  cells. 
  Very 
  characteristic 
  of 
  the 
  

   epidermis 
  is 
  the 
  total 
  absence 
  of 
  epidermal 
  expansions 
  such 
  as 
  

   hairs 
  or 
  thorns, 
  which 
  are 
  so 
  common 
  in 
  most 
  of 
  the 
  other 
  

   Cyperacece. 
  

  

  There 
  is, 
  however, 
  one 
  kind 
  of 
  epidermal 
  expansions 
  which 
  

   our 
  plant 
  has 
  in 
  common 
  with 
  the 
  other 
  Cyperacece, 
  viz 
  : 
  the 
  

   peculiar 
  silicious 
  cones, 
  which 
  are 
  noted 
  to 
  project 
  from 
  the 
  

   bottom 
  of 
  the 
  epidermis-cells 
  and 
  often 
  reaching 
  the 
  superior 
  

   wall. 
  These 
  cones 
  may 
  occur 
  from 
  one 
  to 
  two 
  in 
  each 
  cell 
  

   (Plate 
  IV, 
  iig. 
  3), 
  but 
  they 
  are 
  only 
  present 
  in 
  those 
  strata 
  of 
  

   epidermis 
  which 
  cover 
  the 
  groups 
  of 
  stereome 
  on 
  the 
  dorsal 
  

   face 
  of 
  the 
  leaf-blade. 
  

  

  We 
  have 
  stated 
  above 
  that 
  the 
  epidermis 
  forms 
  an 
  almost 
  

   homogeneous 
  tissue 
  on 
  both 
  faces 
  of 
  the 
  blade, 
  excepting 
  a 
  few 
  

   strata 
  of 
  somewhat 
  narrower 
  cells, 
  covering 
  the 
  mestome- 
  

   bundles, 
  but 
  this 
  divergency 
  in 
  shape 
  is 
  too 
  small 
  to 
  be 
  of 
  any 
  

   importance. 
  We 
  should, 
  however, 
  expect 
  to 
  observe 
  quite 
  a 
  

   considerable 
  variation 
  in 
  some 
  of 
  the 
  epidermal 
  strata, 
  at 
  least 
  

   on 
  the 
  ventral 
  face 
  of 
  the 
  blade. 
  We 
  know 
  from 
  the 
  numer- 
  

   ous 
  and 
  most 
  important 
  writings 
  of 
  Duval-Jouve 
  upon 
  the 
  

   structure 
  of 
  the 
  Cyperacece 
  and 
  the 
  Graminece, 
  that 
  certain 
  

   strata 
  of 
  the 
  epidermis 
  have 
  usually 
  attained 
  a 
  special 
  develop- 
  

   ment, 
  widely 
  different 
  from 
  the 
  other 
  epidermis-cells, 
  and 
  of 
  

   which 
  the 
  function 
  is 
  to 
  facilitate 
  the 
  folding 
  or 
  closing 
  of 
  the 
  

   leaf-blade 
  so 
  as 
  to 
  prevent 
  the 
  surface 
  from 
  being 
  exposed 
  to 
  

   the 
  strong 
  sunlight, 
  thus 
  protecting 
  the 
  leaf 
  against 
  a 
  too 
  rapid 
  

   evaporation. 
  These 
  cells 
  were 
  by 
  Duval-Jouve 
  named 
  "bulli- 
  

   form-cells" 
  (Duval-Jouve: 
  Histotaxie 
  1. 
  c.) 
  and 
  they 
  differ 
  

  

  