﻿664: 
  Mutations 
  

  

  night 
  and 
  day, 
  an 
  irregular 
  jerking 
  movement, 
  

   which 
  has 
  been 
  compared 
  to 
  the 
  movements 
  of 
  

   a 
  semaphore. 
  Desmodium 
  is 
  a 
  papiliona- 
  

   ceous 
  plant 
  and 
  closely 
  allied 
  to 
  the 
  genus 
  

   Hedysarum, 
  which 
  has 
  pinnate 
  leaves 
  with 
  

   numerous 
  pairs 
  of 
  leaflets. 
  Its 
  place 
  in 
  the 
  

   system 
  leaves 
  no 
  doubt 
  concerning 
  its 
  origin 
  

   from 
  pinnate-leaved 
  ancestors. 
  At 
  the 
  time 
  of 
  

   its 
  origination 
  its 
  leaves 
  must 
  have 
  become 
  re- 
  

   duced 
  as 
  to 
  the 
  number 
  of 
  the 
  blades, 
  while 
  the 
  

   size 
  of 
  the 
  terminal 
  leaflet 
  was 
  correspondingly 
  

   increased. 
  

  

  It 
  might 
  seem 
  difficult 
  to 
  imagine 
  this 
  great 
  

   change 
  taking 
  place 
  suddenly. 
  However, 
  we 
  are 
  

   compelled 
  to 
  familiarize 
  ourselves 
  with 
  such 
  hy- 
  

   pothetical 
  assumptions. 
  Strange 
  as 
  they 
  may 
  

   seem 
  to 
  those 
  who 
  are 
  accustomed 
  to 
  the 
  concep- 
  

   tion 
  of 
  continuous 
  slow 
  improvements, 
  they 
  are 
  

   nevertheless 
  in 
  complete 
  agreement 
  with 
  what 
  

   really 
  occurs. 
  Fortunately 
  the 
  direct 
  proof 
  of 
  

   this 
  assertion 
  can 
  be 
  given, 
  and 
  in 
  a 
  case 
  

   which 
  is 
  narrowly 
  related, 
  and 
  quite 
  parallel 
  to 
  

   that 
  of 
  the 
  Desmodium, 
  since 
  it 
  affects 
  a 
  plant 
  

   of 
  the 
  same 
  family. 
  It 
  is 
  the 
  case 
  of 
  the 
  

   monophyllous 
  variety 
  of 
  the 
  bastard-acacia 
  or 
  

   Robinia 
  Pseud-Acacia. 
  In 
  a 
  previous 
  lecture 
  

   we 
  have 
  seen 
  that 
  it 
  originated 
  suddenly 
  in 
  a 
  

   French 
  nursery 
  in 
  the 
  year 
  1855. 
  It 
  can 
  be 
  

   propagated 
  by 
  seed, 
  and 
  exhibits 
  a 
  curious 
  de- 
  

  

  