﻿18 
  T. 
  Holm 
  — 
  Pogonia 
  ophioglossoides. 
  

  

  sesses 
  a 
  ring 
  of 
  stereome 
  around 
  the 
  mestome-bundles, 
  all 
  of 
  

   which 
  are 
  collateral 
  and 
  very 
  regularly 
  arranged 
  in 
  a 
  circle. 
  

   A 
  thin-walled, 
  broken 
  pith 
  occupies 
  the 
  inner 
  part 
  of 
  the 
  

   central-cylinder. 
  

  

  In 
  considering 
  the 
  leaves, 
  these 
  are 
  vertical 
  in 
  P. 
  ophioglos- 
  

   soides, 
  but 
  are 
  kept 
  in 
  a 
  horizontal 
  position 
  in 
  P. 
  vertioillata 
  ; 
  

   they 
  are, 
  nevertheless, 
  almost 
  isolateral 
  in 
  both 
  species, 
  the 
  

   mesophyll 
  being 
  of 
  a 
  homogeneous 
  structure 
  throughout 
  the 
  

   blade 
  ; 
  however, 
  the 
  epidermis 
  shows 
  on 
  the 
  upper 
  face 
  in 
  both 
  

   species 
  to 
  consist 
  of 
  much 
  larger 
  cells 
  than 
  on 
  the 
  lower 
  ; 
  

   moreover, 
  the 
  radial 
  cell-walls 
  of 
  epidermis 
  are 
  straight 
  on 
  the 
  

   upper, 
  but 
  undulate 
  on 
  the 
  lower 
  surface 
  in 
  P. 
  ophioglossoides, 
  

   while 
  they 
  are 
  undulate 
  on 
  both 
  faces 
  in 
  the 
  other 
  species. 
  

   The 
  stomata 
  are 
  restricted 
  to 
  the 
  lower 
  surface, 
  and 
  the 
  

   guard-cells 
  are 
  very 
  prominent 
  in 
  P. 
  ophioglossoides, 
  but 
  not 
  

   so 
  in 
  the 
  other. 
  The 
  mestome-bundles 
  are 
  surrounded 
  by 
  a 
  

   partly 
  green 
  parenchyma-sheath, 
  and 
  only 
  in 
  P. 
  ophioglossoides 
  

   are 
  supported 
  by 
  a 
  small, 
  thin-walled 
  stereome. 
  

  

  In 
  bringing 
  these 
  facts 
  together 
  there 
  appears 
  to 
  exist 
  even 
  

   anatomical 
  characters, 
  by 
  which 
  P. 
  vertioillata, 
  P. 
  ophioglos- 
  

   soides 
  and 
  P. 
  pendula 
  may 
  be 
  distinguished 
  from 
  each 
  other. 
  

   And 
  although 
  it 
  was 
  the 
  main 
  object 
  of 
  this 
  article 
  simply 
  to 
  

   call 
  attention 
  to 
  the 
  presence 
  of 
  root-shoots 
  in 
  Pogonia, 
  we 
  

   naturally 
  felt 
  obliged 
  to 
  examine 
  the 
  systematic 
  position 
  of 
  

   these 
  species, 
  by 
  which 
  we 
  noticed 
  that 
  not 
  all 
  our 
  Pogonice 
  

   are 
  Pogonias 
  in 
  the 
  stricter 
  sense 
  of 
  the 
  word. 
  It 
  would 
  seem 
  

   more 
  natural 
  indeed 
  to 
  adopt 
  the 
  classification 
  proposed 
  by 
  

   Bentham 
  and 
  Hooker, 
  to 
  separate 
  Triphora 
  and 
  Codonorchis 
  

   from 
  Pogonia 
  proper. 
  

  

  Brookland, 
  D. 
  C, 
  October, 
  1899. 
  

  

  Bibliography. 
  

   Brundin, 
  I. 
  A. 
  Z. 
  : 
  Ueber 
  Wurzelsprosse 
  der 
  Listera 
  cordata 
  L. 
  

  

  (Bihang 
  K>Svenska 
  Vet. 
  Akad. 
  Hdlgr., 
  vol. 
  xxi. 
  Stockholm, 
  

  

  1895.) 
  

   Drude, 
  O. 
  : 
  DieBiologie 
  von 
  Monotropa 
  Hypopitys 
  L. 
  und 
  Neottia 
  

  

  Nidus 
  avis 
  L. 
  Goettingen, 
  1 
  873. 
  

   Irmiscb, 
  Thilo 
  : 
  Beitrage 
  zur 
  Biologie 
  und 
  Morphologie 
  der 
  

  

  Orchideen. 
  Leipzig, 
  1853. 
  

   Pfitzer, 
  Ernst 
  : 
  Grundziige 
  einer 
  vergleichenden 
  Morphologie 
  der 
  

  

  Orchideen. 
  Heidelberg, 
  1882, 
  p. 
  142. 
  

   Schacht, 
  Hermann: 
  Ueber 
  die 
  Fortpflanzung 
  der 
  deutschen 
  

  

  Orchideen 
  durch 
  Knospen. 
  (Beitrage 
  zur 
  Anatomie 
  und 
  

  

  Physiologie 
  der 
  Gewachse. 
  Berlin, 
  1854, 
  p. 
  115.) 
  

   Thomas, 
  M. 
  B. 
  : 
  The 
  root-system 
  of 
  Pogonia. 
  (Proceed. 
  Indiana 
  

  

  Acad, 
  of 
  sc, 
  1894.) 
  

   Warming, 
  Eug. 
  : 
  Smaa 
  biologiske 
  og 
  morfologiske 
  Bidrag. 
  (Botan. 
  

  

  Tidsskr. 
  3d 
  series, 
  vol. 
  ii. 
  Kjobenhavn, 
  1877-79, 
  p. 
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