202 
FIFTEENTH REPORT. 
its entire width with the exceptions of the channel and a few areas of 
deep water in other parts of the pond. 
The average depth of that part of the pond covered by this association 
is 4 feet ; the deepest places being near the east shore where the depth 
is about 8 feet ; the shallowest places are not over 2 feet deep. 
Measurements of the accumulated sediment showed a deposit of a foot 
or more near the middle portion of the association. This accumulated 
material no doubt is decayed remains of the dominant plant such as 
Potamogeton nataus on the surface; (Fig. 2) I*, peetinatus and Ceroto- 
phyllum demersum were found growing about 1C inches below the sur- 
face and Ohara sp. was found in abundance growing with its tips sub- 
merged only a few inches. In places the Ohara, is very near the surface 
and in extremely dense masses from 2 to 3 feet thick. 
The following is a list of species in this association: Cerotophyllum 
demersum, Potamogeton lucens, P. nataus. P. peetinatus, Nymph aea 
advena, Oastalia. odorata, Ranunculus aquatilis. 
Continuing from the upper end of the Potamogeton — Ohara association 
for about 2000 feet and extending across the pond from shore to shore 
is the Sparganium — Typha (Burr-seed — Oat-tail) association. 
The water covering this area is much shallower than that of the 
former association. The depth from the surface of the water to the 
surface of the loose and partial liquid sediment of plant material ranges 
from 2 to 8 inches; the depth of the sediment ranges from 12 to 24 
inches. The sediment is not solid but a loose mushy mass of decaying 
plant material. 
The dominant species of this association grow in clumps resembling 
islands and probably in time will form islands by the accumulation of 
debris; these plants having already accumulated sufficient material at 
places to raise the soil surface nearly out of the water. The most 
abundant species is Sparganium eurycarpum, which becomes more and 
more scattered and in smaller groups towards the dam showing that 
it is migrating towards deeper water. Other species growing in the? 
same manner are: Typha americana, Sagitteria latifolia, Polygonum 
hydropiperoides, Scirpus validus and Rumex verticellata. Between these 
clumps are abundant growths of Potamogeton nataus. Cerotophyllum 
demersum and Elodea canadensis besides a number of other scattered 
species. (Fig. 3.) 
Sparganium, the dominant species of this association, has complete 
possession of the areas in which it started and is now growing so dense 
that all other species are kept out. The same is true of the other clumps 
mentioned but they are fewer in number. The conspicuous feature of 
this association is the exclusive grouping of the species. 
The whole upper end of the pond for a distance of about 1200 feet with 
the exception of the stream feeding it is covered with the Gramineae — 
Carex (Grass — Sedge) association. Within the memory of the writer 
this area was open water; but now during the summer it is used for 
pasture. Besides the grasses and sedges there are willows and other 
swamp plants growing quite abundantly. 
Another association of plants in this pond is located in a very ab- 
normal situation. The stumps and logs which were left in the pond 
furnishes this abnormal place for plants to accumulate. As the logs 
