﻿56 
  Elementary 
  Species 
  

  

  produced 
  and 
  the 
  time 
  of 
  flowering 
  were 
  vari- 
  

   able 
  to 
  a, 
  remarkable 
  degree. 
  

  

  Dr. 
  Harsbberger 
  had 
  the 
  kindness 
  to 
  send 
  me 
  

   some 
  dried 
  specimens 
  of 
  the 
  most 
  interesting 
  of 
  

   these 
  types. 
  They 
  show 
  that 
  the 
  peculiarities 
  

   are 
  individual, 
  and 
  that 
  each 
  specimen 
  has 
  its 
  

   own 
  characters. 
  It 
  is 
  very 
  probable 
  that 
  a 
  

   comparative 
  experimental 
  study 
  will 
  prove 
  the 
  

   existence 
  of 
  a 
  large 
  number 
  of 
  elementary 
  spe- 
  

   cies, 
  differing 
  in 
  many 
  points; 
  they 
  will 
  prob- 
  

   ably 
  also 
  show 
  differences 
  in 
  the 
  amount 
  of 
  

   the 
  active 
  chemical 
  substances, 
  especially 
  of 
  

   emetine, 
  which 
  is 
  usually 
  recorded 
  as 
  present 
  in 
  

   about 
  1#, 
  but 
  which 
  will 
  undoubtedly 
  be 
  

   found 
  in 
  larger 
  quantities 
  in 
  some, 
  and 
  in 
  

   smaller 
  quantities 
  in 
  other 
  elementary 
  species. 
  

   In 
  this 
  way 
  the 
  close 
  and 
  careful 
  distinction 
  of 
  

   the 
  really 
  existing 
  units 
  might 
  perhaps 
  prove 
  

   of 
  practical 
  importance. 
  

  

  Macfarlane 
  has 
  studied 
  the 
  beach-plum 
  or 
  

   Prunus 
  maritima, 
  which 
  is 
  abundant 
  along 
  the 
  

   coast 
  regions 
  of 
  the 
  Eastern 
  States 
  from 
  Vir- 
  

   ginia 
  to 
  New 
  Brunswick. 
  It 
  often 
  covers 
  areas 
  

   from 
  two 
  to 
  two 
  hundred 
  acres 
  in 
  extent, 
  some- 
  

   times 
  to 
  the 
  exclusion 
  of 
  other 
  plants. 
  It 
  is 
  most 
  

   prolific 
  on 
  soft 
  drifting 
  sand 
  near 
  the 
  sea 
  or 
  

   along 
  the 
  shore, 
  where 
  it 
  may 
  at 
  times 
  be 
  washed 
  

   with 
  ocean-spray. 
  The 
  fruit 
  usually 
  become 
  

   ripe 
  about 
  the 
  middle 
  of 
  August, 
  and 
  show 
  ex- 
  

  

  