An Ecological Study of Buckeye Lake. 93 



One of the causes of the difference in structure of a Typha 

 angustifoHa society and that of T. latifoha is the difference in 

 depth of water at which they generally grow. The former grows 

 in deeper water than the latter, however, the angustifoHa some- 

 times grows at the very margin of a shore in water but a few 

 incehs in depth. 



Another cause seems to b'e the habit of growth. The culms 

 of T. angustifoHa are massed forming a dense growth, while 

 those of T. latifolia are farther apart permitting better light 

 exposure and freer circulation of air at lower levels. A T. 

 latifolia society always shows stratification, as in the one just 

 described, the Typha forms the upper stratum at a height 5-6 feet 

 above the water, the Sparganium the second at 4-5 feet, the Poly- 

 gonum the third at 2.5-3 ^^^^ and the Roripa americana the fourth 

 at one foot to 15 inches. This species occurs near the margin of 

 the zone. At the extreme outer edge are the Nelumbo and 

 Potamogeton leaves floating on the surface. The two species of 

 Typha form characteristically distinct tussocks separated by open 

 water. However, on the east shore of Buckeye Point a Typha 

 angustifoHa and T. latifolia society are adjacent and in the more 

 open swamp there is a T. angustifoHa society surroimded by a T. 

 latifolia zone. 



The thick root stalks and tough roots of Typha are firmly 

 imbedded in the muck and are not easily uprooted, the thick 

 tough culms and large leaves add materially each year to the 

 surface level, so that it soon becomes high enough to support an 

 amphibious and later a dry land flora. In general the bed of 

 the lake is being built up in this way. Similar but less striking 

 examples can be found in the beds of Polygonum emersum, some 

 of which are quite extensive, as near Castle Island and another 

 in water at a depth of 2 feet, 4 inches just west of Beech Island. 

 Polygonum emersum does not form as dense a growth as the 

 Typhas but the long creeping stems rooting freely at the nodes, 

 and the numerous branches are the cause of the rapid extension 

 of the mat, the tangle of branches catch and hold debris so that 

 the surface soon becomes high enough to permit other plants as 



