﻿PLANTS 
  OF 
  CHINA 
  — 
  WALKER 
  339 
  

  

  waste 
  places 
  belong 
  in 
  this 
  family. 
  A 
  favorite 
  food 
  of 
  the 
  camels 
  

   and 
  other 
  browsing 
  desert 
  animals 
  is 
  the 
  nitre 
  bush 
  {Nitraria 
  scho- 
  

   ber't) 
  of 
  the 
  caltrop 
  family 
  (Zygophyllaceae), 
  which 
  grows 
  in 
  the 
  

   saline 
  soil 
  so 
  common 
  in 
  deserts. 
  It 
  is 
  also 
  an 
  emergency 
  food 
  for 
  man. 
  

   The 
  characteristic 
  central 
  Asiatic 
  desert 
  vegetation 
  is 
  largely 
  com- 
  

   posed 
  of 
  other 
  members 
  of 
  these 
  same 
  families 
  and 
  of 
  the 
  orpine 
  and 
  

   tamarisk 
  families 
  (Crassulaceae 
  and 
  Tamaricaceae, 
  respectively), 
  and 
  

   certain 
  genera 
  and 
  species 
  of 
  the 
  mustard 
  (Cruciferae), 
  pea 
  (Legum- 
  

   inosae, 
  especially 
  the 
  spiny 
  caraganas), 
  pink 
  (Caryophyllaceae), 
  and 
  

   other 
  families 
  as 
  well 
  as 
  euphorbs, 
  sedges, 
  and 
  grasses. 
  The 
  interest- 
  

   ing 
  drug 
  plant 
  Ephedra, 
  rather 
  new 
  in 
  western 
  medicine, 
  but 
  long 
  used 
  

   by 
  the 
  Chinese, 
  is 
  found 
  in 
  the 
  desert. 
  

  

  There 
  are 
  no 
  endemics 
  in 
  this 
  flora, 
  a 
  fact 
  of 
  considerable 
  im- 
  

   portance 
  in 
  considerations 
  of 
  the 
  extent 
  to 
  which 
  the 
  deserts 
  of 
  Asia 
  

   may 
  be 
  man-made 
  and 
  how 
  much 
  they 
  are 
  the 
  result 
  of 
  natural 
  condi- 
  

   tions. 
  Whatever 
  may 
  be 
  the 
  answer 
  to 
  the 
  question 
  of 
  the 
  origin 
  of 
  the 
  

   Gobi 
  Desert, 
  we 
  are 
  very 
  sure 
  that 
  it 
  is 
  gradually 
  extending 
  itself 
  east- 
  

   ward 
  and 
  southward 
  and 
  encroaching 
  on 
  the 
  more 
  habitable 
  lands 
  

   which 
  man 
  needs. 
  Besides 
  the 
  unmistakable 
  historical 
  evidence 
  for 
  

   this 
  progressive 
  desiccation, 
  which 
  is 
  to 
  be 
  found 
  in 
  ancient 
  written 
  

   records, 
  in 
  the 
  reports 
  by 
  people 
  still 
  living, 
  telling 
  of 
  present 
  desola- 
  

   tion 
  where 
  once 
  they 
  saw 
  green 
  fields, 
  and 
  in 
  the 
  ruins 
  of 
  once 
  prosper- 
  

   ous 
  cities 
  now 
  buried 
  in 
  sand, 
  we 
  have 
  botanical 
  evidence 
  in 
  the 
  buried 
  

   and 
  fossilized 
  remains 
  of 
  trees 
  of 
  species 
  which 
  can 
  grow 
  only 
  under 
  

   more 
  moist 
  conditions 
  than 
  now 
  exist. 
  Other 
  evidence 
  is 
  seen 
  in 
  the 
  re- 
  

   mains 
  of 
  Chinese 
  agricultural 
  activity 
  north 
  of 
  the 
  Great 
  Wall, 
  where 
  

   now 
  it 
  is 
  impossible, 
  and 
  in 
  the 
  increasing 
  occurrence 
  of 
  dust 
  storms 
  

   spreading 
  down 
  over 
  China, 
  even 
  as 
  far 
  as 
  Canton. 
  Probably, 
  this 
  pro- 
  

   gressive 
  desiccation 
  is 
  a 
  result 
  of 
  a 
  progressive 
  change 
  in 
  climate, 
  and 
  

   nothing 
  will 
  stop 
  it 
  except 
  a 
  reversal 
  of 
  the 
  trend. 
  In 
  this 
  advance 
  of 
  

   the 
  desert 
  the 
  conifers 
  succumb 
  first, 
  and 
  then 
  the 
  maples, 
  oaks, 
  walnuts, 
  

   and 
  other 
  hardwood 
  trees. 
  The 
  poplars, 
  elms, 
  and 
  willows 
  survive 
  

   the 
  longest, 
  and 
  these 
  constitute 
  the 
  principal 
  trees 
  found 
  today 
  in 
  the 
  

   towns 
  and 
  cities 
  along 
  the 
  Yellow 
  River 
  and 
  the 
  edge 
  of 
  the 
  Gobi 
  

   Desert. 
  In 
  some 
  places 
  one 
  finds 
  the 
  fruitful 
  jujubes 
  or 
  Chinese 
  dates 
  

   cultivated 
  or 
  wild. 
  For 
  people 
  who 
  are 
  accustomed 
  to 
  seeing 
  the 
  best 
  

   of 
  woods 
  used 
  in 
  ship 
  construction 
  it 
  is 
  rather 
  hard 
  to 
  imagine 
  boats 
  

   made 
  of 
  willow 
  planks, 
  but, 
  having 
  no 
  better 
  material 
  available, 
  boat- 
  

   builders 
  on 
  parts 
  of 
  the 
  Yellow 
  River 
  or 
  Hoangho 
  must 
  of 
  necessity 
  

   use 
  this 
  material. 
  

  

  THE 
  LOESS 
  REGION 
  

  

  The 
  dust 
  blown 
  out 
  of 
  the 
  Gobi 
  Desert 
  has 
  throughout 
  the 
  ages 
  

   settled 
  down 
  on 
  regions 
  to 
  the 
  south, 
  building 
  up 
  great 
  deposits 
  of 
  

   the 
  distinctive 
  material 
  called 
  loess. 
  This 
  deposit 
  varies 
  in 
  thickness 
  

  

  