﻿RELATION 
  OF 
  AQUATIC 
  PLANTS 
  TO 
  SUBSTRATUM. 
  501 
  

  

  From 
  these 
  tables 
  it 
  will 
  be 
  noted: 
  

  

  1. 
  The 
  original 
  cuttings 
  in 
  each 
  of 
  the 
  four 
  conditions 
  practically 
  

   ceased 
  to 
  grow 
  in 
  length 
  early 
  in 
  the 
  experiment, 
  adding 
  on 
  the 
  aver- 
  

   age 
  less 
  than 
  3 
  cm. 
  to 
  the 
  original 
  15 
  cm. 
  

  

  2. 
  The 
  new 
  growth 
  consisted 
  of 
  rhizomes 
  and 
  secondary 
  shoots 
  

   arising 
  from 
  them. 
  

  

  3. 
  The 
  plants 
  rooted 
  in 
  soil 
  produced 
  on 
  the 
  average 
  fewer 
  rhizomes 
  

   than 
  those 
  in 
  any 
  of 
  the 
  other 
  three 
  conditions. 
  

  

  4. 
  The 
  average 
  length 
  of 
  the 
  rhizomes 
  arising 
  from 
  the 
  plants 
  rooted 
  

   in 
  soil 
  greatl}^ 
  exceeded 
  that 
  of 
  the 
  rhizomes 
  arising 
  from 
  the 
  plants 
  

   in 
  each 
  of 
  the 
  other 
  three 
  conditions. 
  

  

  5. 
  The 
  average 
  length 
  of 
  the 
  secondary 
  shoots 
  from 
  the 
  plants 
  rooted 
  

   in 
  soil 
  greatly 
  exceeded 
  that 
  of 
  the 
  secondar}^ 
  shoots 
  from 
  the 
  plants 
  

   in 
  the 
  other 
  three 
  conditions. 
  

  

  6. 
  The 
  plants 
  anchored 
  over 
  sand 
  averaged 
  about 
  equall}^ 
  in 
  all 
  

   respects 
  with 
  those 
  anchored 
  over 
  soil. 
  

  

  7. 
  The 
  plants 
  rooted 
  in 
  sand 
  exceeded 
  in 
  all 
  respects, 
  except 
  the 
  

   length 
  of 
  rhizome, 
  the 
  two 
  groups 
  of 
  anchored 
  plants. 
  

  

  In 
  this 
  species 
  the 
  habit 
  of 
  the 
  plant 
  persists 
  whether 
  the 
  cuttings 
  

   be 
  in 
  sand, 
  in 
  soil, 
  or 
  anchored, 
  and 
  the 
  differences 
  arising 
  from 
  the 
  

   differences 
  of 
  environment 
  are 
  quantitative 
  rather 
  than 
  qualitative. 
  

   All 
  of 
  the 
  plants 
  produced 
  rhizomes 
  and 
  secondarj^ 
  shoots. 
  In 
  Rcmiui- 
  

   culus 
  aquatilis 
  tTichophyllm^ 
  however, 
  it 
  will 
  be 
  remembered 
  that 
  the 
  

   natural 
  habit 
  of 
  the 
  plant 
  persisted 
  only 
  in 
  the 
  individuals 
  rooted 
  in 
  

   soil, 
  lateral 
  branches 
  failing 
  to 
  develop 
  in 
  the 
  other 
  groups. 
  

  

  MYRIOPHYLLUM 
  SPICATUM. 
  

  

  Quiet 
  water 
  1 
  to 
  2 
  meters 
  deep 
  and 
  a 
  good 
  loam}^ 
  soil 
  are 
  the 
  favor- 
  

   ite 
  habitat 
  of 
  this 
  species. 
  Isolated 
  specimens 
  occur 
  in 
  shallow 
  water 
  

   and 
  sandy 
  soil 
  where 
  they 
  have 
  been 
  washed 
  as 
  drifting 
  fragments, 
  

   but 
  the 
  plants 
  do 
  not 
  establish 
  themselves 
  under 
  such 
  conditions. 
  

   Long 
  branching 
  roots 
  are 
  developed, 
  but 
  root 
  hairs 
  have 
  never 
  been 
  

   found. 
  Roots 
  ma}^ 
  arise 
  at 
  almost 
  an}'^ 
  node, 
  and 
  numerous 
  stem 
  

   branches 
  arise 
  to 
  give 
  the 
  plant 
  a 
  bushy 
  form. 
  The 
  leaves 
  are 
  finely 
  

   dissected, 
  the 
  stem 
  strong 
  and 
  flexible, 
  so 
  that 
  the 
  plant 
  seems 
  adapted 
  

   to 
  rougher 
  water 
  than 
  that 
  in 
  which 
  it 
  usuall}^ 
  occurs. 
  I 
  have 
  never 
  

   found 
  it 
  occup3Mng 
  any 
  considerable 
  area 
  or 
  so 
  abundant 
  as 
  to 
  suggest 
  

   the 
  exclusion 
  of 
  other 
  species 
  b}^ 
  it. 
  As 
  roots 
  develop 
  abundantl}^ 
  

   but 
  do 
  not 
  have 
  root 
  hairs, 
  it 
  was 
  considered 
  desirable 
  to 
  determine 
  

   whether 
  oi- 
  not 
  the 
  plant 
  is 
  dependent 
  upon 
  its 
  attachment 
  to 
  the 
  soil 
  

   for 
  optimum 
  growth. 
  

  

  Experiment 
  No. 
  5. 
  — 
  The 
  location 
  and 
  conditions 
  remain 
  as 
  in 
  experiments 
  3 
  and 
  4. 
  

   The 
  duration 
  in 
  this 
  case 
  is 
  one 
  month, 
  from 
  July 
  10 
  to 
  August 
  10. 
  Terminal 
  cut- 
  

   tings 
  15 
  cm. 
  in 
  length 
  and 
  without 
  roots 
  were 
  selected 
  from 
  thrifty 
  river 
  plants. 
  

  

  On 
  August 
  10 
  the 
  general 
  appearance 
  of 
  the 
  plants 
  was 
  as 
  follows: 
  The 
  two 
  groups 
  

   of 
  anchored 
  plants 
  were 
  about 
  alike 
  in 
  all 
  respects 
  and 
  had 
  numerous 
  roots 
  arising 
  from 
  

  

  