﻿Double 
  Adaptations 
  437 
  

  

  horticulture 
  under 
  the 
  varietal 
  name 
  of 
  Hede- 
  

   ra 
  Helix 
  arborea. 
  

  

  Manifestly 
  this 
  classification 
  is 
  as 
  nearly 
  

   right 
  as 
  that 
  of 
  the 
  two 
  varieties 
  of 
  the 
  water- 
  

   persicaria. 
  Going 
  one 
  step 
  further, 
  we 
  meet 
  

   with 
  the 
  very 
  interesting 
  case 
  of 
  alpine 
  plants. 
  

   The 
  vegetation 
  of 
  the 
  higher 
  regions 
  of 
  moun- 
  

   tains 
  is 
  commonly 
  called 
  alpine, 
  and 
  the 
  plants 
  

   show 
  a 
  large 
  number 
  of 
  common 
  features, 
  dif- 
  

   ferentiating 
  them 
  from 
  the 
  flora 
  of 
  lower 
  sta- 
  

   tions. 
  The 
  mountain 
  plants 
  have 
  small 
  and 
  

   dense 
  foliage, 
  with 
  large 
  and 
  brightly-colored 
  

   flowers. 
  The 
  corresponding 
  forms 
  of 
  the 
  low- 
  

   lands 
  have 
  longer 
  and 
  weaker 
  stems, 
  bearing 
  

   their 
  leaves 
  at 
  greater 
  distances, 
  the 
  leaves 
  

   themselves 
  being 
  more 
  numerous. 
  The 
  alpine 
  

   forms, 
  if 
  perennial, 
  have 
  thick, 
  strongly 
  de- 
  

   veloped 
  and 
  densely 
  branched 
  rootstocks 
  with 
  

   heavy 
  roots, 
  in 
  which 
  a 
  large 
  amount 
  of 
  food- 
  

   material 
  is 
  stored 
  up 
  during 
  the 
  short 
  summer, 
  

   and 
  is 
  available 
  during 
  the 
  long 
  winter 
  months 
  

   of 
  the 
  year. 
  

  

  Some 
  species 
  are 
  peculiar 
  to 
  such 
  high 
  al- 
  

   titudes, 
  while 
  many 
  forms 
  from 
  the 
  lowlands 
  

   have 
  no 
  corresponding 
  type 
  on 
  the 
  mountains. 
  

   But 
  a 
  large 
  number 
  of 
  species 
  are 
  common 
  to 
  

   both 
  regions, 
  and 
  here 
  the 
  difference 
  of 
  course 
  is 
  

   most 
  striking. 
  Lotus 
  corniculatus 
  and 
  Cala- 
  

   mintha 
  Acinos, 
  Calluna 
  vulgaris 
  and 
  Campa- 
  

  

  