﻿T. 
  Holm 
  — 
  Pogonia 
  ophioglossoides. 
  15 
  

  

  one 
  {I 
  1 
  ) 
  are 
  still 
  fresh 
  and 
  the 
  apex 
  of 
  the 
  rhizome 
  is 
  terminated 
  

   by 
  a 
  bud, 
  surrounded 
  by 
  the 
  scale-like 
  leaf 
  Z\ 
  There 
  appears 
  

   thus 
  to 
  be 
  a 
  regular 
  succession 
  of 
  green 
  and 
  scale 
  like 
  leaves, 
  

   but 
  the 
  most 
  common 
  case 
  is, 
  however, 
  that 
  the 
  first 
  leaf 
  of 
  

   the 
  root-shoots 
  is 
  scale-like 
  instead 
  of 
  being 
  a 
  green, 
  assimilat- 
  

   ing 
  one. 
  

  

  In 
  passing 
  to 
  describe 
  the 
  root-system, 
  it 
  may 
  be 
  stated 
  at 
  

   once, 
  that 
  the 
  main 
  propagation 
  of 
  our 
  plant, 
  P. 
  ophioglossoides, 
  

   seems 
  to 
  take 
  place 
  by 
  means 
  of 
  root-shoots. 
  All 
  the 
  speci- 
  

   mens 
  which 
  were 
  collected 
  by 
  the 
  writer 
  in 
  a 
  Sphagnum- 
  

   swamp 
  near 
  Washington, 
  D. 
  C, 
  were 
  developed 
  from 
  roots, 
  

   and 
  the 
  same 
  was, 
  also, 
  the 
  case 
  with 
  a 
  number 
  of 
  specimens 
  

   from 
  a 
  similar 
  locality 
  in 
  Maine, 
  kindly 
  furnished 
  by 
  Mr. 
  M. 
  

   L. 
  Fernald 
  of 
  the 
  Gray 
  herbarium, 
  Harvard 
  University. 
  

  

  This 
  is 
  the 
  more 
  surprising 
  since, 
  so 
  far, 
  but 
  very 
  few 
  of 
  the 
  

   Orchidece 
  are 
  known 
  to 
  propagate 
  in 
  this 
  manner, 
  the 
  only 
  

   ones 
  being 
  : 
  JVeottia 
  Nidus 
  avis 
  (L), 
  Cephalanthera 
  rubra 
  (L), 
  

   Epipactis 
  microphylla 
  (Ehrh.) 
  and 
  Listera 
  cordata 
  L., 
  all 
  from 
  

   Europe; 
  besides 
  that 
  we 
  have, 
  also, 
  observed 
  a 
  similar 
  develop- 
  

   ment 
  of 
  root-shoots 
  in 
  Pogonia 
  verticillata 
  (fig. 
  4). 
  It 
  is 
  very 
  

   likely 
  that 
  similar 
  cases 
  may 
  be 
  observed 
  in 
  P. 
  divaricata 
  and 
  

   P. 
  affinis, 
  but 
  our 
  dried 
  material, 
  the 
  only 
  one 
  being 
  at 
  hand, 
  

   was 
  not 
  preserved 
  very 
  carefully 
  so 
  as 
  to 
  demonstrate 
  the 
  root- 
  

   system. 
  It 
  appears 
  as 
  if 
  this 
  formation 
  of 
  root-shoots 
  is 
  con- 
  

   fined 
  to 
  such 
  genera, 
  in 
  which 
  no 
  tuberous 
  roots 
  occur, 
  and 
  in 
  

   which 
  no 
  tuberous 
  or 
  bulbous 
  stem-internodes 
  are 
  developed. 
  

   We 
  might 
  suppose 
  that 
  several 
  of 
  the 
  other 
  Orchidece 
  really 
  

   exhibit 
  the 
  same 
  manner 
  of 
  propagation, 
  but 
  only 
  those 
  of 
  

   which 
  the 
  root-system 
  is 
  similar 
  to 
  that 
  of 
  Pogonia 
  or 
  JVeottia 
  / 
  

   it 
  is, 
  no 
  doubt, 
  a 
  character 
  common 
  to 
  the 
  species 
  of 
  Listera, 
  

   Cephalanthera, 
  Epipactis, 
  and 
  perhaps 
  also 
  to 
  Cypripedium, 
  

   at 
  least 
  in 
  some 
  of 
  those 
  roots 
  which 
  run 
  in 
  a 
  horizontal 
  direc- 
  

   tion 
  close 
  beneath 
  the 
  surface 
  of 
  the 
  ground. 
  Among 
  the 
  

   dicotyledonous 
  orders 
  many 
  species 
  propagate 
  in 
  this 
  way, 
  and 
  

   we 
  need 
  only 
  to 
  refer 
  to 
  the 
  long 
  lists 
  of 
  such 
  plants, 
  contributed 
  

   by 
  Warming 
  and 
  Wittrock."* 
  However, 
  root-shoots 
  may 
  be 
  

   of 
  very 
  different 
  kind, 
  and 
  Professor 
  Wittrock 
  has 
  proposed 
  

   three 
  categories 
  in 
  regard 
  to 
  the 
  circumstances 
  under 
  which 
  

   they 
  may 
  occur 
  and 
  in 
  regard 
  to 
  their 
  importance 
  to 
  the 
  mother- 
  

   plant: 
  reparative, 
  additional 
  and 
  necessary.f 
  The 
  root-shoots 
  

  

  * 
  For 
  references 
  consult 
  the 
  bibliography 
  appended 
  to 
  this 
  article. 
  

  

  f 
  Reparative 
  root-shoots 
  being 
  such 
  which 
  develop 
  only 
  in 
  cases 
  where 
  the 
  

   root 
  becomes 
  broken 
  away 
  from 
  the 
  mother-plant, 
  and 
  the 
  mother-shoot 
  thus 
  lie- 
  

   comes 
  injured 
  or 
  killed: 
  Taraxacum, 
  Centaur 
  ea. 
  Scabiosa 
  and 
  Bunias 
  oritntale 
  for 
  

   instance. 
  Additional 
  root-shoots 
  develop, 
  on 
  the 
  contrary, 
  spontaneously 
  upon 
  

   roots 
  of 
  uninjured 
  specimens 
  hence 
  forming 
  a 
  more 
  or 
  less 
  important 
  addition 
  to 
  

   the 
  reproduction 
  of 
  the 
  individual: 
  the 
  majority 
  of 
  plants 
  with 
  root-shoots 
  Neces- 
  

   sary 
  are 
  such 
  as 
  constitute 
  a 
  part 
  of 
  the 
  normal, 
  morphological 
  development 
  of 
  

   certain 
  plants, 
  e. 
  g. 
  Pyrola 
  uniflora, 
  Monotropa 
  Hypopitys, 
  Cirsium 
  arvense, 
  etc. 
  

  

  