92 Proceedings of the Ohio State Academy of Science. 



Typha latifolia, 7 Peltandra virginca were scattered over the 

 southern half. The willows in the center were not more than 2 

 feet tall, stunted and much branched. The sediment clinging to 

 the tips of the branches showed that they had been entirely sub- 

 merged. The ground cover was almost wholly composed of 

 Elocharis acicularis, no other sedges or grasses could be found and 

 but a few Bidens, Hibiscus and Impatiens seedlings. The peat 

 shelf surrounding the island and with its surface just under water 

 bore everywhere a copious growth of Heteranthera dubia, which 

 had also invaded the mud flat. Fig. 30 is a photograph of the 

 islet taken Aug. 4, 191 1. 



IV. Islands originating in shallozv water thru the gradual 

 upbuilding of the siirface by the ac cumulation of vegetal remains, 

 as illustrated in a Typha tussock. 



In the eastern part of the lake from Custer's Point to the 

 southeastern extremity are many Typha tussocks of both Typha 

 angustifolia and T. latifolia, which differ strikingly in the struc- 

 ture of the flora, but which gradually pass from the one type to 

 the other. 



One of each type of tussock was studied. The Typha 

 angustifolia tussock formed a pure society about 24 feet in 

 diameter and grew in water 3 feet deep at the margin and 2j/4 

 feet in the center. The culms were fully ten feet tall and bloom- 

 ing freely. Only at the margin on the leeward side were there 

 any other plants. Here, June 24, 191 1, were a few Potamogeton 

 lonchites and small Castalia tuberosa leaves with Lemna trisulca 

 on the surface of the water. 



The Typha latifolia tussock was 50 feet south of the T. 

 angustifolia. Surrounding it in water from 3.5-3 feet deep was a 

 zone of Nelumbo lutea, Potamogeton pectinatus, P. lonchites, P. 

 natans and Polygonum emersum, the last nearest the Typha, 

 which occupied a zone about 18 feet broad. In the outer margin 

 of this zone were Nelumbo leaves. Associated with the Typha 

 throughout the zone was Sparganium eurycarpum, Polygonum 

 emersum and Roripa americana. The water decreased in depth 

 towards the center where it was 9 inches. Here was a clump of 

 Hibiscus moscheutos with Lemna trisulca floating on the water. 



