﻿454 
  JOURNAI, 
  OP 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  20 
  

  

  writer 
  in 
  an 
  earlier 
  number 
  of 
  this 
  Journal. 
  ^° 
  Recasting 
  the 
  two 
  analy- 
  

   ses 
  above 
  by 
  allotting 
  FeO 
  to 
  TiOo 
  to 
  form 
  ilmenite 
  (FeO.Ti02) 
  the 
  

   mineral 
  composition 
  in 
  terms 
  of 
  rutile 
  and 
  ilmenite 
  is 
  : 
  

  

  I 
  II 
  

  

  Rutile 
  • 
  94.80 
  59.92 
  

  

  Ilmenite 
  4.71 
  39.67 
  

  

  Rest 
  .62 
  .44 
  

  

  100.13 
  100.03 
  

  

  The 
  analysis 
  in 
  column 
  II 
  clearly 
  shows 
  a 
  mixture 
  of 
  rutile 
  and 
  il- 
  

   menite, 
  in 
  which 
  rutile 
  is 
  in 
  largest 
  amount. 
  Although 
  a 
  thin 
  section 
  

   of 
  this 
  particular 
  specimen 
  was 
  not 
  examined, 
  it 
  is 
  not 
  improbable 
  

   that 
  some 
  of 
  the 
  ilmenite 
  may 
  have 
  been 
  secondary. 
  

  

  BOTANY. 
  — 
  The 
  genus 
  Culcita.^ 
  William 
  R. 
  Maxon, 
  National 
  

   Museum. 
  

  

  The 
  tribe 
  Dicksonieae, 
  one 
  of 
  the 
  three 
  groups 
  of 
  Cyatheaceae 
  or 
  

   tree 
  ferns, 
  is 
  usually 
  regarded 
  as 
  consisting 
  of 
  three 
  genera: 
  Dick- 
  

   sonia, 
  Cibotium, 
  and 
  Balantmm, 
  all 
  represented 
  in 
  both 
  hemispheres. 
  

   The 
  distinctions 
  between 
  Dicksonia 
  and 
  Cibotium 
  are 
  fairly 
  pronounced, 
  

   and 
  both 
  names 
  are 
  currently 
  applied 
  in 
  their 
  proper 
  sense. 
  Balantium, 
  

   though 
  showing 
  indusium 
  characters 
  similar 
  to 
  those 
  of 
  Dicksonia, 
  is 
  

   habitually 
  very 
  different 
  from 
  either, 
  and 
  its 
  recognition 
  as 
  a 
  valid 
  genus 
  

   is 
  general. 
  The 
  name 
  Balantium, 
  however, 
  is 
  technically 
  a 
  synonym 
  

   of 
  Dicksonia 
  and 
  must 
  be 
  supplanted 
  by 
  Culcita, 
  as 
  shown 
  below. 
  

   The 
  distinctive 
  characters 
  of 
  the 
  genera 
  of 
  Dicksonieae 
  were 
  stated 
  

   briefly 
  by 
  the 
  writer 
  a 
  few 
  years 
  ago 
  in 
  a 
  popular 
  article 
  on 
  the 
  tree 
  

   ferns 
  of 
  North 
  America^ 
  and 
  the 
  name 
  Culcita 
  was 
  there 
  employed 
  in 
  

   the 
  present 
  sense, 
  without, 
  however, 
  a 
  statement 
  of 
  the 
  reasons 
  for 
  

   substituting 
  it 
  for 
  Balantium. 
  

  

  The 
  genus 
  Dicksonia 
  was 
  described 
  by 
  L'Heritier 
  in 
  1788 
  ^ 
  with 
  two 
  

   species: 
  D. 
  arborescens, 
  from 
  St. 
  Helena, 
  and 
  D. 
  culcita, 
  from 
  San 
  

   Miguel, 
  one 
  of 
  the 
  Azores, 
  both 
  being 
  proposed 
  as 
  new. 
  The 
  form_er 
  

   is 
  an 
  arborescent 
  plant 
  and, 
  except 
  for 
  its 
  temporary 
  reference 
  to 
  

   Balantium 
  by 
  Hooker 
  in 
  1838, 
  has 
  been 
  consistently 
  retained 
  as 
  the 
  

  

  >o 
  Watson, 
  Thomas 
  L. 
  This 
  Journal 
  2: 
  431^34. 
  1912. 
  

  

  ' 
  Published 
  by 
  permission 
  of 
  the 
  Secretary 
  of 
  the 
  Smithsonian 
  Institution. 
  Received 
  

   October 
  9, 
  1922. 
  

  

  2 
  Report 
  Smiths. 
  Inst. 
  1911: 
  463-491. 
  pi. 
  1-15. 
  1912. 
  

  

  3 
  Sert. 
  Angl. 
  30. 
  1788. 
  

  

  