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  INTRODUCTION 
  TO 
  BOTANY 
  

  

  material, 
  with 
  a 
  minimum 
  amount 
  of 
  decayed 
  material 
  from 
  

   plant 
  and 
  animal 
  life. 
  If 
  the 
  water 
  level 
  is 
  below 
  such 
  soils, 
  

   the 
  water 
  runs 
  away 
  and 
  there 
  is 
  left 
  in 
  the 
  soil 
  little 
  available 
  

   moisture 
  and 
  little 
  available 
  organic 
  matter. 
  In 
  sandy 
  soils 
  

   the 
  rock 
  has 
  been 
  broken 
  by 
  weathering 
  processes, 
  sometimes 
  

   aided 
  by 
  the 
  action 
  of 
  plant 
  life, 
  until 
  the 
  rock 
  particles 
  are 
  

   small. 
  The 
  coarseness 
  of 
  the 
  sand 
  depends 
  upon 
  the 
  extent 
  

   to 
  which 
  the 
  rock 
  particles 
  are 
  broken. 
  They 
  may 
  have 
  been 
  

   crushed 
  and 
  worn 
  into 
  pieces 
  so 
  small 
  that 
  clay 
  is 
  formed 
  and 
  

   the 
  separate 
  grains 
  can 
  be 
  seen 
  only 
  by 
  magnification. 
  

  

  Water 
  may 
  be 
  in 
  the 
  soil 
  either 
  in 
  the 
  spaces 
  between 
  soil 
  

   particles 
  or 
  adhering 
  to 
  the 
  particles. 
  As 
  the 
  soil 
  becomes 
  

   finer 
  its 
  ability 
  to 
  retain 
  water 
  increases. 
  This 
  is 
  due 
  to 
  two 
  

   facts 
  : 
  first, 
  that 
  water 
  adheres 
  to 
  the 
  surface 
  of 
  the 
  soil 
  parti- 
  

   cles; 
  second, 
  that 
  the 
  larger 
  the 
  number 
  of 
  particles 
  within 
  

   a 
  given 
  volume 
  the 
  greater 
  is 
  the 
  surface 
  exposed. 
  1 
  Also, 
  soil 
  

   with 
  fine-grained 
  sand 
  will 
  hold 
  the 
  products 
  of 
  decayed 
  plant 
  

   and 
  animal 
  life 
  better 
  than 
  rocky 
  soils. 
  Soils 
  are 
  classified 
  

   into 
  many 
  kinds, 
  according 
  to 
  the 
  size 
  and 
  nature 
  of 
  the 
  rock 
  

   material 
  and 
  the 
  nature 
  of 
  the 
  plant 
  and 
  animal 
  material 
  con- 
  

   tained. 
  The 
  leading 
  kinds 
  are 
  ///w/v//// 
  soils, 
  containing 
  small 
  

   pebbles 
  which 
  usually 
  show 
  by 
  their 
  form 
  and 
  sometimes 
  by 
  

   their 
  markings 
  the 
  kind 
  of 
  treatment 
  they 
  have 
  undergone; 
  

   sandy 
  soils, 
  in 
  which 
  the 
  rock 
  material 
  is 
  more 
  uniform 
  and 
  

   has 
  gone 
  farther 
  in 
  its 
  reduction 
  ; 
  day 
  soils, 
  whose 
  particles 
  are 
  

   so 
  small 
  and 
  fit 
  together 
  so 
  compactly 
  that 
  the 
  rock 
  origin 
  

   is 
  not 
  very 
  evident 
  ; 
  peaty 
  soils, 
  containing 
  comparatively 
  little 
  

   rock 
  material 
  but 
  much 
  more 
  of 
  the 
  products 
  of 
  partial 
  decay 
  

   of 
  plant 
  and 
  animal 
  bodies. 
  There 
  are 
  all 
  possible 
  gradations 
  

   between 
  these 
  different 
  kinds 
  of 
  soils. 
  The 
  chemical 
  and 
  

   physical 
  nature 
  of 
  the 
  rock-and-humus 
  content 
  of 
  soils 
  has 
  

   much 
  to 
  do 
  with 
  their 
  relation 
  to 
  plant 
  life. 
  

  

  1 
  This 
  may 
  be 
  shown 
  by 
  calculating 
  tin- 
  surface 
  of 
  a 
  cube 
  ten 
  inches 
  in 
  

   diameter, 
  then 
  cutting 
  it 
  into 
  one-inch 
  cubes 
  and 
  calculating 
  the 
  surf 
  aces 
  of 
  

   these, 
  and 
  then 
  comparing 
  the 
  surface 
  of 
  the 
  original 
  cube 
  with 
  the 
  sum 
  of 
  

   the 
  surfaces 
  of 
  those 
  made 
  from 
  it. 
  

  

  