An Ecological Study of Buckeye Lake. 77 



Secondary species : 



Ceratophylluni demersum Brachythecium plumosum 



Spirogyra sp. Riccia fluitans 



Lemna trisulca Ilysanthes gratioloides 



Cladaphora sp. Sium cicutaefolium 

 Spirodela polyrhyza 



This society forms a dense zone 60 feet broad, and extends 

 from water 8 inches deep to wholly emersed surface. Thirty- 

 five feet of the zone covers a mnd flat which is submerged at 

 the normal water level. The Polygonum has advanced into the 

 Nelumbo. Towards the inner margin the Nelumbo is 2 feet tall 

 and fruiting freely. 



A short distance west of the belt studied, the Polygonum 

 has entirely outdistanced the Nelumbo, replacing society i with 

 a Polygonum zone external to a mixed Polygonum-Nelumbo 

 zone. 



Of the secondary species, Brachythecium plumosum is the 

 most abundant, especially on the exposed mud surface, quite 

 large patches of which are covered by a pure growth of the 

 moss. The Riccia is also a conspicuous member of the ground 

 cover. The herbs are very sparse. 



Towards the west of the median line of the belt is, 

 3. A Polygonum-Xelumbo-Typha society. A zone com- 

 posed of societies from the I and II associations. 

 Principal species : 



Polygonum emersum 

 Xelumbo lutea 

 Typha latifolia 

 Secondary species : 



Spirodela polyrhyza 

 Lemna trisulca 

 Cladophora sp. 

 Ceratophylluni demersum 



The secondary s]:)ecies, which are normally floating jjlants, 

 are stranded on the mud and form but a thin covering. The 



