﻿200 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  8 
  

  

  Sign 
  of 
  Extinc- 
  Twinning 
  Inferred 
  

  

  Refractive 
  indices 
  elonga- 
  tion 
  plane 
  habit 
  — 
  

  

  Lengthwise 
  Crosswise 
  tion 
  angles 
  may 
  show 
  elongated 
  on 
  

  

  « 
  1.490 
  /3 
  1.555 
  7 
  1-650 
  .. 
  0° 
  Lengthwise 
  axis 
  6 
  

  

  1.555 
  « 
  1.490 
  7 
  1.650 
  ± 
  o-13° 
  Cmsswise 
  or 
  

  

  lengthwise 
  axis 
  a 
  

  

  7 
  1.650. 
  a 
  1.490 
  /3 
  1.555 
  + 
  0-30° 
  Diagonally 
  axis 
  c 
  

  

  7 
  1.650 
  a 
  1.490 
  /3 
  1.555 
  + 
  0-6 
  1/2° 
  Lengthwise 
  zone 
  of 
  e 
  : 
  6 
  

  

  These 
  data 
  are 
  being 
  applied 
  to 
  the 
  study 
  of 
  the 
  crystals 
  of 
  calcium 
  

   oxalate 
  occurring 
  in 
  official 
  crude 
  drugs 
  and 
  other 
  plants, 
  a 
  report 
  on 
  

   which 
  will 
  appear 
  elsewhere. 
  

  

  BOTANY. 
  — 
  Twc 
  new 
  species 
  of 
  Acanthospermum 
  from 
  the 
  Galapagos 
  

   Islands} 
  S. 
  F. 
  Blake, 
  Bureau 
  of 
  Plant 
  Industry. 
  

  

  Several 
  months 
  ago 
  I 
  published- 
  a 
  revision 
  of 
  the 
  genus 
  Acantho- 
  

   spermum, 
  a 
  small 
  group 
  of 
  Asteraceae 
  closely 
  related 
  to 
  Melampodium, 
  

   from 
  which 
  it 
  is 
  distinguished 
  technically 
  by 
  the 
  presence 
  of 
  spines 
  

   or 
  hooked 
  prickles 
  on 
  the 
  indurated 
  phyllaries 
  which 
  envelop 
  the 
  ray 
  

   achenes. 
  Of 
  the 
  eight 
  species 
  there 
  described 
  the 
  most 
  aberrant 
  is 
  

   Acanthospermum 
  lecocarpoides 
  Robins. 
  & 
  Greenm., 
  the 
  sole 
  member 
  of 
  

   the 
  Section 
  Lecocarpopsis, 
  which 
  is 
  distinguished 
  from 
  the 
  two 
  other 
  

   sections 
  of 
  the 
  genus 
  by 
  its 
  pinnatifid 
  leaves, 
  plump 
  trigonous-turbin- 
  

   ate 
  fruit 
  bearing 
  spines 
  only 
  around 
  the 
  broadly 
  rounded 
  apex, 
  and 
  

   comparatively 
  large 
  rays.^ 
  The 
  species, 
  seen 
  by 
  me 
  only 
  in 
  two 
  

   collections 
  from 
  Hood 
  Island, 
  Galapagos 
  Archipelago, 
  is 
  remarkable 
  

   for 
  its 
  rather 
  close 
  resemblance 
  in 
  every 
  feature 
  but 
  the 
  fruit 
  to 
  the 
  

   monotypic 
  genus 
  Lecocarpus 
  Decaisne, 
  which 
  is 
  confined 
  to 
  Chatham 
  

   and 
  Charles 
  Islands 
  of 
  the 
  same 
  group. 
  

  

  After 
  the 
  paper 
  above 
  referred 
  to 
  had 
  been 
  turned 
  in 
  for 
  publication, 
  

  

  1 
  found 
  at 
  the 
  Gray 
  Herbarium 
  two 
  sheets 
  of 
  Acanthospermumy 
  

   collected 
  by 
  Alban 
  Stewart 
  on 
  Chatham 
  and 
  Gardner-near-Hood 
  

   Islands, 
  which 
  appeared 
  to 
  represent 
  two 
  new 
  species 
  of 
  the 
  Section 
  

   Lecocarpopsis. 
  Through 
  the 
  kindness 
  of 
  Miss 
  Alice 
  Eastwood, 
  I 
  

   was 
  able 
  to 
  supplement 
  these 
  two 
  sheets 
  by 
  the 
  extensive 
  series 
  of 
  

   mounted 
  and 
  unmounted 
  duplicates 
  of 
  the 
  same 
  two 
  numbers 
  in 
  the 
  

   herbarium 
  of 
  the 
  California 
  Academy 
  of 
  Sciences. 
  vStudy 
  of 
  this 
  

   material, 
  amounting 
  in 
  all 
  to 
  42 
  sheets, 
  shows 
  that 
  it 
  unquestionably 
  

   represents 
  two 
  new 
  forms 
  of 
  the 
  Section 
  Lecocarpopsis. 
  Since 
  these 
  

  

  1 
  Received 
  March 
  5, 
  1922. 
  

  

  2 
  Contr. 
  U. 
  S. 
  Nat. 
  Herb. 
  20: 
  383-392, 
  pi. 
  23. 
  1921. 
  

  

  ' 
  The 
  extreme 
  corky-woody 
  thickening 
  of 
  the 
  fruiting 
  phvllaries 
  at 
  maturity 
  is 
  also 
  

   characteristic 
  of 
  this 
  section 
  of 
  the 
  genus. 
  

  

  