﻿124: 
  T. 
  Holm 
  — 
  Studies 
  in 
  the 
  Cyjperacece. 
  

  

  very 
  much 
  from 
  the 
  surrounding 
  cells 
  in 
  regard 
  to 
  their 
  size 
  

   and 
  shape. 
  They 
  are 
  often 
  developed 
  as 
  vesicles 
  with 
  a 
  rather 
  

   thick 
  and 
  strongly 
  cuticularized 
  outer-wall, 
  and 
  show 
  a 
  great 
  

   tendency 
  to 
  collapse, 
  when 
  exposed 
  to 
  excessive 
  drought, 
  

   while 
  they 
  rapidly 
  swell 
  up 
  again, 
  when 
  brought 
  in 
  contact 
  

   with 
  moisture. 
  These 
  peculiar 
  cells 
  are, 
  as 
  a 
  rule, 
  located 
  

   on 
  the 
  superior 
  face 
  of 
  the 
  leaf-blade 
  and 
  they 
  are 
  most 
  

   often 
  to 
  be 
  observed 
  above 
  the 
  midrib, 
  but 
  also 
  between 
  

   some 
  of 
  the 
  larger 
  mestome-bundles 
  in 
  several 
  genera, 
  espe- 
  

   cially 
  in 
  the 
  broad-leaved 
  species. 
  

  

  It 
  is 
  easily 
  understood, 
  that 
  being 
  located 
  where 
  they 
  are, 
  

   these 
  cells 
  by 
  collapsing 
  naturally 
  force 
  the 
  blade 
  to 
  become 
  

   folded 
  either 
  as 
  simply 
  " 
  condu 
  plicate 
  " 
  or 
  as 
  " 
  convolute." 
  In 
  

   the 
  genus 
  Garex, 
  of 
  the 
  species 
  which 
  have 
  been 
  examined, 
  

   this 
  form 
  of 
  cells 
  has 
  never 
  been 
  observed 
  to 
  be 
  missing. 
  We 
  

   have 
  figured 
  the 
  most 
  common 
  shape 
  and 
  size, 
  which 
  these 
  

   bulliform 
  cells 
  attain 
  in 
  Garex, 
  e. 
  g. 
  figure 
  5, 
  which 
  is 
  from 
  G. 
  

   mreseens 
  Muhl., 
  a 
  species 
  with 
  leaves 
  of 
  ordinary 
  width, 
  and 
  

   which 
  grows 
  in 
  localities 
  not 
  exposed 
  to 
  excessive 
  drought 
  or 
  

   moisture. 
  In 
  some 
  species, 
  which 
  inhabit 
  places 
  exposed 
  to 
  

   heavy 
  winds, 
  and 
  which 
  are 
  especially 
  characteristic 
  of 
  the 
  

   sand-dune 
  vegetation, 
  the 
  bulliform-cells 
  are 
  especially 
  devel- 
  

   oped 
  and 
  are 
  even 
  supported 
  by 
  several 
  strata 
  of 
  similar, 
  but 
  

   smaller 
  cells, 
  all 
  constituting 
  a 
  typic 
  closing-apparatus 
  for 
  the 
  

   leaf-blade. 
  Figure 
  6 
  shows 
  such 
  layers 
  of 
  bulliform 
  cells 
  from 
  

   the 
  leaf 
  of 
  G. 
  trinercis 
  Degl., 
  a 
  common 
  sand-sedge 
  from 
  the 
  

   west 
  coast 
  of 
  Europe. 
  The 
  very 
  narrow-leaved 
  Varices 
  have, 
  

   on 
  the 
  other 
  hand, 
  not 
  the 
  bulliform 
  cells 
  so 
  well 
  differentiated, 
  

   as 
  for 
  instance 
  in 
  G. 
  exilis 
  Dew. 
  (fig. 
  4), 
  besides 
  similar 
  marsh- 
  

   sedges, 
  as 
  G 
  diceca 
  L., 
  G. 
  gynocrates 
  Wormskj., 
  etc. 
  

  

  But 
  our 
  G. 
  Fvaseri 
  is 
  entirely 
  destitute 
  of 
  any 
  such 
  bulli- 
  

   form 
  cells 
  on 
  either 
  side 
  of 
  the 
  blade, 
  which 
  is 
  the 
  more 
  sur- 
  

   prising 
  when 
  we 
  consider 
  the 
  extraordinary 
  width 
  of 
  the 
  

   leaves 
  ; 
  the 
  plant 
  seems, 
  therefore, 
  to 
  be 
  very 
  poorly 
  adapted 
  

   for 
  existing 
  outside 
  of 
  the 
  damp 
  and 
  shaded 
  ravines 
  where 
  it 
  

   usually 
  occurs. 
  

  

  In 
  considering 
  now 
  the 
  structure 
  of 
  the 
  other 
  tissues 
  which 
  

   compose 
  the 
  leaf, 
  our 
  plant 
  does 
  not 
  differ 
  in 
  any 
  essential 
  

   respect 
  from 
  the 
  other 
  species 
  of 
  Garex. 
  The 
  mesophyll 
  

   forms 
  a 
  homogeneous 
  tissue 
  all 
  through 
  the 
  blade, 
  and 
  it 
  con- 
  

   sists 
  of 
  polygonal 
  cells, 
  which 
  are 
  closely 
  packed 
  on 
  both 
  faces 
  

   of 
  the 
  leaf, 
  while 
  the 
  central 
  part 
  of 
  the 
  leaf-blade 
  is 
  traversed 
  

   by 
  broad 
  lacunes, 
  which 
  are 
  only 
  separated 
  from 
  each 
  other 
  by 
  

   the 
  mestome-bundles 
  and 
  the 
  adjoining 
  mesophyll. 
  

  

  Very 
  distinct 
  from 
  the 
  mesophyll 
  is 
  the 
  thin-walled 
  paren- 
  

   chyma-sheath, 
  which 
  partly 
  surrounds 
  the 
  mestome-bundle, 
  at 
  

   least 
  on 
  the 
  sides, 
  extending 
  from 
  the 
  stereome 
  of 
  the 
  superior 
  

  

  