Development of the Vegetation of New York State 99 
bed was settling to the bottom as if prematurely weighted 
down by the hme. 
But one or more species of Chara (stonewort) show par- 
ticularly well the réle of rapid additions to the marl sub- 
stratum. The Chara beds in question are in from one to 
four feet of water. The plants form a close mat looking not 
unlike a well kept turf. Lime accumulates upon them in 
such quantity that by midsummer the beds become gray and 
the whole mat being now brittle and heavily weighted breaks 
down as did the Potamogetons above mentioned. 
3. Aquatic Vegetation With Floating or Exposed Leaves or 
Emerged Stems. 
Certain species of submerged plants of group 2 grow 
habitually in shallow water and, among these, some which as 
the water level falls or the plant elongates have exposed 
leaves. Thus in Potamogeton natans when floating leaves 
are developed (and in water only a foot or two in depth the 
leaves are nearly all floating) they are different in shape and 
structure from the submerged ones; indeed their greater 
spread must retard the further development of submerged 
leaves by shading. The fullest expression of this idea of the 
floating leaf and with it the harmony between plant form and 
shallow water habitat is found in the water lily type. Recall 
in this connection the maximum expression of this in the 
remarkable Victoria regia of the Amazon. It is not the aim 
here to try to show how this representative type of shallow 
water vegetation is qualified to replace the submerged types, 
although the inference as to the broad floating leaves and 
shutting off of light from the water beneath insinuates itself, 
but certainly in shallow water whether on mineral bottom or 
sedimentary deposits or on a substratum built up by aquatic 
vegetation and mineral debris, a ‘‘ water lily zone” is ex- 
pected in our lakes and ponds except of course where the 
force of wind and waves would prevent. We regard it here 
as the natural successor to the submerged zone. Other 
erowth forms appear in this shallow water zone also. Arrow 
arum (Peltandra virginica L.) is one. Its large leaves are 
