﻿420 
  Transactions.-— 
  'Butany. 
  

  

  of 
  tlie 
  rostellum 
  become 
  converted 
  into 
  a 
  milky 
  and 
  excessively 
  viscid 
  

   substance, 
  wliilo 
  tlie 
  whole 
  surface 
  of 
  tbe 
  stigma 
  secretes 
  abundantly 
  a 
  

   clear, 
  viscid 
  matter, 
  and 
  a 
  drop 
  of 
  sweet 
  fluid 
  is 
  secreted 
  at 
  the 
  base 
  of 
  

   the 
  column. 
  

  

  The 
  action 
  of 
  the 
  parts 
  is 
  exceedingly 
  simple. 
  An 
  insect 
  alighting 
  on 
  

   the 
  labellum 
  weighs 
  it 
  down 
  very 
  easily, 
  and 
  thus 
  gains 
  access 
  to 
  the 
  nectar 
  

   at 
  its 
  base. 
  The 
  elasticity 
  of 
  the 
  labellum, 
  however, 
  tends 
  to 
  keep 
  it 
  press» 
  

   ing 
  against 
  the 
  column, 
  and 
  thus 
  compels 
  the 
  insect 
  to 
  brush 
  against 
  tho 
  

   viscid 
  rostellum. 
  The 
  pollinia 
  are 
  very 
  easily 
  withdrawn 
  by 
  an 
  upAvard 
  

   movement, 
  as 
  can 
  be 
  seen 
  by 
  introducing 
  a 
  needle 
  or 
  pencil 
  point, 
  and 
  

   touching 
  the 
  rostellum 
  in 
  withdrawing 
  it, 
  when 
  one 
  or 
  more 
  of 
  the 
  pollinia 
  

   ■will 
  be 
  withdrawn 
  with 
  it. 
  The 
  lateral 
  lobes 
  of 
  the 
  labellum 
  and 
  the 
  guiding 
  

   ridges 
  on 
  its 
  surface 
  W'ould 
  prevent 
  an 
  insect 
  reaching 
  the 
  nectar 
  without 
  

   touching 
  the 
  rostellum 
  when 
  leaving 
  the 
  floAver 
  : 
  and 
  any 
  insect 
  entering 
  

   another 
  flower 
  Avith 
  pollinia 
  on 
  its 
  head, 
  could 
  not 
  fail 
  to 
  leaA^e 
  these 
  on 
  the 
  

   stigma. 
  By 
  inserting 
  a 
  fly, 
  tliis 
  action 
  was 
  easily 
  seen, 
  all 
  four 
  pollinia 
  

   being 
  AAathdrawn, 
  AA'ith 
  their 
  caudicle 
  glued 
  over 
  the 
  insect's 
  right 
  eye. 
  Out 
  

   of 
  tAventy-two 
  flowers 
  examined, 
  only 
  five 
  had 
  theu' 
  pollinia 
  removed 
  from 
  

   the 
  anther 
  cases, 
  but 
  as 
  the 
  plant 
  Avas 
  groAving 
  on 
  a 
  veranda 
  aAvay 
  from 
  

   its 
  native 
  habitat, 
  this 
  Avas 
  no 
  criterion. 
  I 
  regret 
  that 
  I 
  did 
  not 
  fertilize 
  

   any 
  of 
  the 
  flowers 
  on 
  this 
  plant 
  AA'ith 
  their 
  OAvn 
  pollen. 
  Those 
  fertilized 
  by 
  

   pollen 
  from 
  other 
  floAvers 
  on 
  the 
  same 
  plant 
  produced 
  fine 
  capsules. 
  

  

  Tribe 
  Arethuse^. 
  

   (3.) 
  Corysaiitlics 
  m 
  acrantlia 
  , 
  

  

  Both 
  this 
  species 
  and 
  C. 
  rkularis 
  were 
  examined 
  by 
  me, 
  but 
  the 
  floAvers 
  

  

  are 
  almost 
  identical 
  in 
  structure, 
  the 
  difference 
  not 
  affecting 
  the 
  relations 
  of 
  

  

  the 
  parts. 
  They 
  are 
  very 
  striking 
  in 
  appearance, 
  owing 
  to 
  their 
  lurid 
  

  

  purple 
  colour, 
  and 
  the 
  long 
  tAvisted 
  sepals 
  and 
  petals, 
  which 
  give 
  them 
  an 
  

  

  extraordinary 
  resemblance 
  to 
  a 
  large 
  spider 
  sitting 
  on 
  a 
  leaf. 
  The 
  upper 
  

  

  sepal 
  is 
  large, 
  prominent, 
  and 
  helmet-shaped, 
  and 
  projects 
  forAvard 
  over 
  the 
  

  

  floAA'er. 
  The 
  labellum 
  is 
  large 
  and 
  involute, 
  almost 
  semi-cylindrical, 
  Avith 
  

  

  its 
  external 
  margin 
  fimbriated 
  and 
  expanded 
  doAvnAvards 
  into 
  a 
  longish 
  tip. 
  

  

  It 
  is 
  not 
  attached 
  continuously 
  at 
  its 
  base. 
  On 
  each 
  side 
  of 
  the 
  floAver, 
  

  

  when 
  in 
  bud, 
  a 
  small 
  slit 
  is 
  seen, 
  Avhich 
  widens 
  by 
  an 
  expansion 
  of 
  the 
  

  

  margin 
  (which 
  is 
  thus 
  caused 
  to 
  arch 
  slightly 
  outAvards) 
  into 
  a 
  small 
  circular 
  

  

  aperture. 
  By 
  the 
  contact 
  of 
  the 
  in-turned 
  edges 
  of 
  the 
  labellum, 
  and 
  the 
  

  

  overlapping 
  ot 
  the 
  upper 
  sepal, 
  a 
  horizontal 
  aperture 
  is 
  left 
  in 
  the 
  mouth 
  of 
  

  

  the 
  floAver, 
  which 
  bends 
  at 
  right-angles 
  a 
  little 
  Avay 
  in, 
  and 
  opens 
  into 
  a 
  

  

  tolerably 
  large 
  cavity. 
  Placed 
  quite 
  at 
  the 
  bottom 
  of 
  this 
  is 
  the 
  short, 
  

  

  thick 
  column, 
  lying 
  almost 
  horizontally 
  in 
  C. 
  ricularis, 
  and 
  somcAvhat 
  more 
  

  

  erect 
  in 
  C. 
  macrantha. 
  The 
  stigmatic 
  cavity 
  is 
  deep, 
  and 
  on 
  its 
  posterior 
  

  

  