﻿108 
  T. 
  Holm 
  — 
  Studies 
  in 
  the 
  Cyperacefje. 
  

  

  narrower 
  groups 
  than 
  in 
  the 
  healthy 
  ones, 
  wlien 
  considered 
  in 
  

   transverse 
  sections. 
  The 
  mesophyll 
  consists 
  of 
  a 
  homogeneous, 
  

   colorless 
  tissue 
  in 
  the 
  diseased 
  leaves 
  and 
  is 
  traversed 
  by 
  laciines 
  

   of 
  considerable 
  width, 
  while 
  this 
  same 
  tissue, 
  in 
  the 
  healthy 
  

   leaf, 
  is 
  differentiated 
  into 
  a 
  compact, 
  chlorophyll-bearing 
  tissue 
  

   on 
  the 
  upper 
  face 
  and 
  a 
  more 
  open 
  pneumatical 
  tissue 
  below 
  ; 
  

   lacunes 
  are 
  present, 
  but 
  they 
  are 
  relatively 
  smaller. 
  In 
  con- 
  

   sidering 
  the 
  mestome 
  bundles, 
  these 
  show 
  the 
  same 
  structure 
  

   in 
  both 
  leaves, 
  but 
  are 
  more 
  numerous 
  and 
  much 
  broader 
  in 
  

   those 
  diseased 
  ; 
  a 
  parenchyma- 
  and 
  a 
  mestome-sheath 
  are 
  

   present 
  in 
  both 
  and 
  show 
  the 
  same 
  difference 
  in 
  size, 
  as 
  observed 
  

   in 
  the 
  other 
  tissues. 
  A 
  study 
  of 
  the 
  silica-skeleton 
  demon- 
  

   strated 
  the 
  fact, 
  that 
  this 
  matter 
  was 
  almost 
  absent 
  in 
  the 
  

   infested 
  leaves 
  in 
  contrast 
  to 
  the 
  others. 
  

  

  While 
  our 
  specimens 
  thus 
  possessed 
  both 
  normally 
  and 
  

   abnormally 
  developed 
  leaves, 
  it 
  seemed 
  as 
  if 
  the 
  rhizome 
  had 
  

   undergone 
  some 
  modification 
  in 
  its 
  entire 
  length. 
  The 
  bark- 
  

   parenchyma 
  appeared, 
  however, 
  to 
  be 
  perfectly 
  healthy, 
  repre- 
  

   senting 
  an 
  outer 
  and 
  inner 
  zone 
  having 
  cells 
  thick-walled 
  and 
  

   thin-walled 
  respectively 
  and 
  filled 
  with 
  starch 
  ; 
  there 
  was, 
  also, 
  

   an 
  endodermis 
  with 
  the 
  inner 
  walls 
  somewhat 
  thickened. 
  By 
  

   examining 
  the 
  interior 
  part 
  of 
  the 
  rhizome, 
  the 
  mestome- 
  

   bundles, 
  these 
  were 
  scattered 
  in 
  the 
  thin 
  -walled, 
  starch 
  -bearing 
  

   fundamental 
  tissue, 
  and 
  they 
  represented 
  as 
  commonly 
  noticed 
  

   both 
  collateral 
  and 
  perihadromatic 
  bundles. 
  Yery 
  noticeable 
  

   were 
  the 
  narrow 
  vessels, 
  besides 
  the 
  very 
  weakly 
  developed 
  

   stereome 
  around 
  each 
  of 
  the 
  mestome-bundles. 
  When 
  com- 
  

   pared 
  with 
  a 
  rhizome 
  of 
  a 
  healthy 
  specimen, 
  the 
  difference 
  

   was 
  very 
  striking 
  and 
  most 
  pronounced 
  by 
  the 
  narrow 
  lumen 
  

   of 
  the 
  various 
  vessels. 
  

  

  Although 
  the 
  roots 
  showed 
  no 
  signs 
  of 
  any 
  abnormal 
  devel- 
  

   opment, 
  we 
  thought 
  desirable 
  to 
  describe 
  their 
  structure, 
  which 
  

   exhibited 
  some 
  points 
  that 
  may 
  be 
  of 
  interest 
  for 
  comparative 
  

   studies 
  of 
  these 
  organs. 
  Their 
  structure 
  is 
  as 
  follows. 
  Inside 
  

   the 
  epidermis 
  are 
  about 
  four 
  layers 
  of 
  thin 
  walled, 
  but 
  per- 
  

   sistent 
  bark-parenchyma, 
  which 
  surrounds 
  the 
  inner 
  bark, 
  the 
  

   cells 
  of 
  which 
  show 
  the 
  usual 
  tangential 
  collapsing, 
  excepting 
  

   the 
  two 
  innermost 
  strata. 
  There 
  is, 
  besides, 
  a 
  typical 
  endo- 
  

   dermis, 
  of 
  which 
  the 
  cell-walls 
  are 
  slightly 
  thickened 
  all 
  

   around. 
  The 
  pericambium 
  is 
  very 
  thin-walled 
  and 
  demon- 
  

   strates 
  the 
  fact 
  (figs. 
  6 
  and 
  T) 
  that 
  it 
  is 
  not 
  interrupted 
  by 
  all 
  

   the 
  proto-hadrome 
  vessels. 
  Out 
  of 
  thirteen 
  of 
  these 
  vessels 
  

   two 
  were 
  observed 
  to 
  lie 
  within 
  the 
  pericambium, 
  separated 
  by 
  

   this 
  from 
  endodermis. 
  In 
  some 
  cases 
  (fig. 
  6) 
  there 
  was 
  not 
  

   onl}^ 
  one 
  proto-hadrome 
  vessel 
  developed, 
  but 
  two, 
  and 
  con- 
  

   trary 
  to 
  the 
  rule, 
  as 
  it 
  appears, 
  the 
  inner 
  was 
  the 
  smaller. 
  The 
  

   leptome 
  showed 
  no 
  divergence 
  from 
  that 
  of 
  other 
  roots 
  and 
  

  

  