204 
FIFTEENTH REPORT. 
r>. No doubt 75% of the plant species found on the stumps and logs 
were started from seeds carried by birds, 
b. Potamogeton and Cerotophvllum are the least abundant near the 
dam but increase in abundance towards the upper end of the 
pond, becoming most abundant where the Sparganium becomes 
thick. 
7. Sparganium is migrating towards the dam and has reached the 
middle of the pond. 
8. In the Potamogeton — Chara association the sediment is one foot 
deep. In the Sparganium — Tvpha association it is two feet deep. 
The present indications are that at the rate this pond is and has been 
filling the last 30 years, another period of equal length will entirely fill 
it with plant remains and sediment. 
