﻿Geology 
  and 
  Mineralogy. 
  -119 
  

  

  always 
  be 
  visible. 
  The 
  walls 
  bounding 
  the 
  figures 
  and 
  the 
  cracks 
  

   are 
  usually 
  parallel 
  to 
  common 
  crystal 
  faces 
  on 
  the 
  mineral. 
  

   The 
  symmetry 
  of 
  the 
  figure 
  is 
  concordant 
  with 
  that 
  of 
  the 
  min- 
  

   eral. 
  The 
  papers 
  are 
  illustrated 
  with 
  many 
  figures 
  and 
  by 
  well- 
  

   executed 
  plates 
  showing 
  reproductions 
  of 
  photographs 
  of 
  the 
  

   "tear-figures." 
  w. 
  e. 
  f. 
  

  

  6. 
  A 
  Meteorite 
  from 
  Tertiary 
  Deposits. 
  — 
  It 
  is 
  stated 
  that 
  a 
  

   mass 
  of 
  meteoric 
  iron, 
  found 
  in 
  1901 
  in 
  the 
  "white-channel 
  

   gravels" 
  near 
  Dawson, 
  Klondike, 
  is 
  probably 
  of 
  Pliocene 
  age 
  

   or 
  older 
  (R. 
  G. 
  McDonnell). 
  Another 
  mass, 
  inferred 
  to 
  have 
  

   formed 
  part 
  of 
  the 
  same 
  shower, 
  was 
  found 
  in 
  1905 
  in 
  the 
  same 
  

   region. 
  The 
  masses 
  have 
  been 
  examined 
  by 
  R. 
  A. 
  A. 
  Johnston 
  

   and 
  are 
  preserved 
  in 
  the 
  Museum 
  of 
  the 
  Geological 
  Survey 
  of 
  

   Canada 
  at 
  Ottawa.— 
  Nature, 
  March 
  27, 
  1919, 
  p. 
  69. 
  

  

  7. 
  The 
  Living 
  Cycads; 
  by 
  Charles 
  Joseph 
  Chamberlain. 
  

   Small 
  12mo, 
  172 
  pp. 
  with 
  90 
  illustrations 
  in 
  the 
  text. 
  Univer- 
  

   sity 
  of 
  Chicago 
  Press, 
  1919 
  (price 
  $1.50). 
  — 
  In 
  this 
  little 
  book 
  is 
  

   given 
  an 
  outline 
  of 
  studies 
  extending 
  over 
  nearly 
  twenty 
  years. 
  

   There 
  is 
  first 
  an 
  account 
  at 
  once 
  readable 
  and 
  entertaining 
  of 
  

   the 
  cycads 
  and 
  cycad 
  collecting 
  in 
  the 
  chief 
  habitats 
  in 
  Mexico, 
  

   South 
  Africa, 
  and 
  Australia. 
  The 
  life-history 
  and 
  phytogeny 
  

   follow. 
  The 
  book 
  and 
  style 
  are 
  attractive 
  and 
  would 
  afford 
  a 
  

   model 
  for 
  the 
  treatment 
  of 
  various 
  other 
  plant 
  groups. 
  Green- 
  

   house 
  study 
  of 
  the 
  cycads, 
  at 
  least, 
  has 
  little 
  of 
  the 
  living 
  interest 
  

   disclosed 
  by 
  their 
  field 
  study. 
  

  

  Those 
  reading 
  this 
  book 
  need 
  only 
  go 
  back 
  twenty-five 
  years 
  to 
  

   recall 
  the 
  signal 
  progress 
  made 
  in 
  the 
  study 
  of 
  the 
  cycads. 
  A 
  

   small 
  living 
  group, 
  only 
  a 
  few 
  new 
  species 
  have 
  been 
  added 
  ; 
  but 
  

   nearly 
  all 
  the 
  critical 
  studies 
  following 
  the 
  earlier 
  anatomical 
  

   notes 
  of 
  Mettenius, 
  Miquel 
  and 
  Yon 
  Mohl 
  belong 
  to 
  the 
  past 
  

   twenty-five 
  years. 
  The 
  first 
  stimulus 
  to 
  study 
  of 
  the 
  group 
  came 
  

   from 
  the 
  discovery 
  of 
  motile 
  ciliated 
  sperms 
  in 
  Ginkgo 
  in 
  1896, 
  

   shortly 
  followed 
  by 
  their 
  observation 
  in 
  Cycas 
  by 
  Ikeno. 
  The 
  

   next 
  event 
  of 
  significance 
  was 
  of 
  course 
  the 
  discovery 
  of 
  the 
  

   cyeadeoid 
  flower 
  and 
  foliage 
  in 
  1899. 
  

  

  Various 
  primitive 
  features 
  of 
  the 
  cycads 
  have 
  long 
  been 
  more 
  

   or 
  less 
  clearly 
  recognized. 
  But 
  these 
  more 
  persistent 
  studies 
  of 
  

   structure, 
  reproduction, 
  and 
  the 
  antithesis 
  to 
  cones 
  seen 
  in 
  the 
  

   cyeadeoids, 
  all 
  go 
  far 
  to 
  give 
  botanists 
  a 
  renewed 
  confidence 
  in 
  

   their 
  discussions 
  of 
  some 
  of 
  the 
  most 
  fundamental 
  problems 
  of 
  

   seed 
  plant 
  evolution. 
  Speaking 
  of 
  the 
  relationships 
  between 
  the 
  

   cycads 
  and 
  fossil 
  cycads 
  [cycadeoids], 
  Professor 
  Chamberlain 
  

   says 
  : 
  

  

  "The 
  university 
  zone 
  of 
  the 
  Northern 
  Hemisphere 
  has 
  been 
  

   studied 
  with 
  considerable 
  care, 
  and 
  the 
  amount 
  of 
  Triassic 
  mate- 
  

   rial 
  obtained 
  has 
  not 
  been 
  encouraging; 
  but 
  the 
  tropics 
  and 
  

   Southern 
  Hemisphere 
  may 
  yield 
  material 
  which 
  will 
  solve 
  the 
  

   whole 
  problem. 
  The 
  immense 
  amount 
  of 
  fossil 
  material 
  secured 
  

  

  