﻿ROOTS 
  AND 
  THEIR 
  RELATION 
  TO 
  PLANTS 
  29 
  

  

  rainfalls 
  of 
  the 
  regions 
  where 
  

   these 
  plants 
  grow. 
  Others, 
  as 
  

   the 
  mesquite 
  of 
  the 
  extreme 
  

   southwest, 
  have 
  roots 
  that 
  pen- 
  

   etrate 
  into 
  the 
  earth 
  to 
  extra- 
  

   ordinary 
  depths 
  until 
  they 
  reach 
  

   moist 
  soil. 
  Still 
  others 
  --for 
  

   example, 
  many 
  South 
  African 
  

   plants 
  (fig. 
  20), 
  some 
  wild 
  

   morning-glories, 
  and 
  the 
  big- 
  

   root 
  1 
  of 
  the 
  Pacific 
  coast 
  - 
  

   have 
  fleshy 
  roots 
  in 
  which 
  much 
  

   water 
  is 
  stored. 
  

  

  28. 
  Water 
  roots. 
  Most 
  aquatic 
  

   perennials, 
  like 
  the 
  cat-tails, 
  ar- 
  

   rowheads, 
  pickerel 
  weeds, 
  pond 
  

   lilies, 
  and 
  many 
  grasses 
  and 
  

   sedges, 
  form 
  mainly 
  earth 
  roots. 
  

   On 
  the 
  other 
  hand, 
  some 
  plants 
  

   not 
  aquatics 
  --for 
  example, 
  many 
  willows 
  can 
  develop 
  roots 
  

   indifferently 
  either 
  

  

  in 
  earth 
  or 
  in 
  water. 
  

  

  Willows 
  growing 
  .^, 
  H 
  

  

  along 
  a 
  brook 
  usu- 
  

   ally 
  send 
  great 
  

   numbers 
  of 
  roots 
  

   into 
  the 
  earth, 
  and 
  

   also 
  produce 
  a 
  mul- 
  

   titude 
  of 
  fibrous 
  

   roots 
  which 
  dangle 
  

   in 
  the 
  water. 
  Cut- 
  

   tings 
  of 
  Wander- 
  FIG. 
  21. 
  Duckweed, 
  a 
  floating 
  aquatic 
  plant 
  

   ing 
  Jew 
  (Zebrincf), 
  At 
  left, 
  top 
  view 
  of 
  single 
  plant 
  8 
  times 
  natural 
  size 
  ; 
  

  

  o-praninm 
  ( 
  Pclarao- 
  at 
  ri 
  S 
  ht 
  ' 
  S 
  rou 
  P 
  of 
  three 
  individuals 
  of 
  another 
  species 
  

   & 
  _ 
  y 
  represented 
  as 
  floating, 
  with 
  roots 
  hanging 
  vertically. 
  

  

  nium}, 
  and 
  many 
  Three 
  and 
  one-half 
  times 
  natural 
  size. 
  After 
  Prant] 
  

  

  1 
  Echinocystis. 
  

  

  FIG. 
  20. 
  A 
  desert 
  Pelargonium 
  

   (closely 
  related 
  to 
  the 
  common 
  so- 
  

   called 
  geraniums) 
  

  

  Note 
  the 
  scanty 
  leaf 
  surface 
  and 
  the 
  

   fleshy 
  root 
  and 
  hase 
  of 
  the 
  stem, 
  con- 
  

   taining 
  much 
  water 
  and 
  reserve 
  food. 
  

   After 
  Andrews 
  

  

  