96 College of Forestry 
rock formation is most significant. Walcott’ and others 
ascribe to such organisms the role of forming massive lime- 
stone deposits. 
(3) Floating Plants of Groups Higher than Algae. 
In our latitude this group comprises especially the duck- 
weed family among angiosperms, Salviniaceae of the pterid- 
ophytes and certain Ricciaceae of the /Lepaticae or liverwort 
group. Duckweed should be especially familiar because of 
its abundance in small ponds or quiet shore waters where it 
forms a close cover over the water and materially affects 
the penetration of light below the water surface. The more 
bulky vegetation such as is formed by the water hyacinth in 
southern streams will be recalled in this connection. 
2. Submerged Aquaties. 
The developmental sequence of static vegetation, 1. e. 
plants anchored to the substratum by roots (rhizoids in the 
case of stoneworts), really begins with this stage in which 
the whole plant is under water of varying depth and with 
roots (or rhizoids) and often root stocks imbedded in the 
accumulating, loose, oozy, organic soil of the lake or stream 
or tide flat bottom. Its dynamic significance hes partly 
of course in the bulkiness of the vegetation, familiar as 
heavy banks of pondweed (Potamogetons) or of beds of 
“ditch grass” (Hlodea canadensis) of shallow lake waters, 
but especially in binding the loose bottom sediment into a 
firmer matrix. The occupation of lake bottom soil is faeil- 
itated by the perennial habits of the imbedded parts and the 
1 Waleott, C. D. Pre-Cambrian Algonkian Algal Flora. Smithsonian 
Miscel. Coll., 64:No. 2, 1914. In this paper, p. 87, notes taken by 
Dr. C. A. Davis on the calcareous deposits in Green and Round Lakes 
near Kirkville, Onondaga county are quoted. From these, the follow- 
ing: “In Green Lake, considerable spaces along the shore have de- 
posits of tufa which extend out into the lake from the shore for as 
much as twenty feet or more in places, forming perpendicular or over- 
hanging sub-aquatie cliffs or terraces.” Again, “In two places, logs 
of white cedar (Thuja) were noted which were completed imbedded in 
the solid faces of the cliff and projecting from them.” 
See also Dr. John M. Clarke’s paper on “ Water Biscuit ” (notably 
from Canandaigua Lake). Bull. N. Y. State Mus., No. 39, vol. 8, 1900. 
