417 
A few filaments observed Noy. 23, 1909, Jan. 9, 1910. Never observed 
in fruit. 
Oedogonium undulatum Brebisson. 
The most abundant alga in the pond. It is present throughout the 
year. It was observed fruiting sexually on Noy. 16, 1909, and April 113 
1910. After the sexual season in the spring the plants decline in vigor. 
There are enormous numbers of oospores present in the water at this 
“time. 
Chaetophora pisiformis Roth. 
Common at all seasons on stems. 
Typha latifolia L. 
This is the most conspicuous plant in the pond. It covered the shal- 
lower two-thirds of the pond in 1908 and has since increased to about three- 
fourths of the total area. It is from this plant that most of the vegetable 
debris on the bottom of the pond is derived. 
In 1910 shoots appeared frem the stolons Mar..24. Seeds began ger- 
minating April 8, flowers were formed in June and seeds were ripe early in 
September. 
The seeds which fali in the water are usually blown to the lee side 
of the pond where they collect in dense masses. This results in very 
weak seedlings during germination. <A slight reduction of level is fatal 
at this period. Besides this, the margin where these seeds germinate is 
already oceupied by parent plants. From these facts, it is evident that the 
seeds of Typha are very inefficient in increasing the number of plants in 
a pond where it is alrendy established. ‘The increase is derived chiefly 
from buds from the stolons. The seeds, while ill adapted to this function, 
are very efficient in securing the introduction of the species into ponds 
unoccupied by it. On a spike 150 mm. long, I have estimated the number 
of seeds to be 27,000. How far they may be carried by wind is conjectural, 
and on that account this efficiency can not be reduced to figures. The 
chances of introduction of any wind-blown seed is inverse to the distance 
from the center of distribution, but the proportion is unknown. Certainly 
it is greater in the direction of the prevailing winds than in any other. It 
may be observed that if the seeds were distributed evenly over a circle 
whose radius is one mile (the distance to the nearest pond) a seed from 
each spike would have approximately five chances in six of hitting a pond 
of that size (70 ft. in diameter) placed anywhere in this circle. 
[27—26988 ] 
