﻿EELATTON 
  OF 
  AQUATIC 
  PLANTS 
  TO 
  SUBSTRATUM. 
  

  

  105 
  

  

  them 
  as 
  to 
  the 
  amount 
  of 
  vegetation 
  each 
  can 
  support. 
  To 
  secure 
  natural 
  conditions 
  

   a 
  platform 
  was 
  built 
  in 
  the 
  lake 
  near 
  the 
  laboratory 
  and 
  on 
  this 
  platform 
  were 
  placed 
  

   three 
  glass 
  aquaria. 
  The 
  tops 
  of 
  the 
  aquaria 
  were 
  about 
  15 
  cm. 
  below 
  the 
  lake 
  level. 
  

   Each 
  aquarium 
  contained 
  one 
  type 
  of 
  soil 
  as 
  a 
  substratum 
  of 
  about 
  10 
  cm. 
  depth. 
  

   In 
  each 
  aquarium 
  10 
  plants 
  of 
  Vallisneria 
  and 
  10 
  of 
  Chara 
  were 
  planted. 
  This 
  mate- 
  

   rial 
  was 
  carefully 
  selected, 
  the 
  individuals 
  being 
  of 
  uniform 
  size, 
  placed 
  in 
  water 
  of 
  

   favorable 
  depth, 
  and 
  exposed 
  to 
  natural 
  light 
  conditions. 
  

  

  The 
  following 
  table 
  gives 
  the 
  meclftnical 
  analysis 
  of 
  the 
  three 
  types 
  of 
  soil 
  as 
  deter- 
  

   mined 
  by 
  the 
  Bureau 
  of 
  Soils, 
  U. 
  S. 
  Department 
  of 
  Agriculture. 
  The 
  results 
  are 
  

   expressd 
  in 
  percentages: 
  

  

  Analyses 
  of 
  soils 
  tested 
  for 
  groivlh. 
  of 
  Vallisneria 
  and 
  Chara. 
  

  

  The 
  following 
  notes, 
  taken 
  by 
  Prof. 
  F. 
  C. 
  Newcombe, 
  furnish 
  a 
  general 
  characteri- 
  

   zation 
  of 
  the 
  three 
  soils 
  as 
  determined 
  by 
  observation: 
  

  

  No. 
  1. 
  Brownish 
  gray 
  throughout, 
  cohesive, 
  very 
  fine 
  texture, 
  little 
  if 
  any 
  grit 
  to 
  

   the 
  feeling, 
  abundant 
  plant 
  remains 
  in 
  fine 
  fibres, 
  no 
  gas 
  in 
  hydrochloric 
  acid. 
  

  

  No. 
  2. 
  Blackish 
  gray, 
  gritty, 
  rather 
  coarse, 
  

   sandy, 
  coliesive, 
  fibrous 
  with 
  plant 
  remains, 
  

   moHuscan 
  shells 
  sparse, 
  yielding 
  much 
  gas 
  

   in 
  hydrochloric 
  acid. 
  

  

  No. 
  3. 
  Bluish 
  clay, 
  blotched 
  with 
  buff, 
  

   hard 
  and 
  coherent, 
  almost 
  no 
  grit, 
  few 
  plant 
  

   remains, 
  'little 
  gas 
  in 
  hydrochloric 
  acid. 
  

   After 
  the 
  action 
  of 
  acid 
  a 
  granular 
  sediment 
  

   remains 
  composed 
  apparently 
  of 
  quartz 
  

   grains. 
  

  

  The 
  experiment 
  shows 
  that 
  soil 
  

   No. 
  1 
  supports 
  the 
  most 
  growth, 
  soil 
  

   No. 
  2 
  next, 
  and 
  soil- 
  No. 
  3 
  the 
  least 
  

   growth. 
  The 
  same 
  relation 
  holds 
  for 
  

   Chara 
  as 
  for 
  Vallisneria. 
  The 
  rela- 
  

   tive 
  size 
  of 
  representative 
  plants 
  

   from 
  each 
  of 
  the 
  three 
  aquaria 
  is 
  

   shown 
  in 
  figures 
  3, 
  4, 
  and 
  5. 
  The 
  

   plants 
  were 
  pressed 
  and 
  mounted, 
  

   the 
  photographs 
  being 
  taken 
  from 
  

   the 
  herbarium 
  sheet. 
  

  

  Chara. 
  being 
  difficult 
  to 
  subject 
  to 
  linear 
  measurement, 
  the 
  air-dry 
  

   weight 
  of 
  the 
  10 
  plants 
  in 
  each 
  case 
  was 
  taken, 
  and 
  this 
  gives 
  a 
  fair 
  

   index 
  of 
  the 
  relative 
  amount 
  of 
  growth 
  in 
  each 
  soil. 
  In 
  No. 
  1 
  it 
  was 
  

   2.175 
  grams; 
  in 
  No. 
  2, 
  1.31:5 
  grams; 
  in 
  No. 
  3, 
  O.650 
  grams. 
  

  

  