80 Proceedings of the Ohio State Academy of Science. 



Secondary species : 



Rosa Carolina Hibiscus moscheutos 



Sambucus canadensis Solanum dulcamara 



Micrampeles lobata Homalocenchrus oryzoides 



Polygonum acre Galium trifidum 



Erechtites hieracifolia Carex lupulina 



Scutellaria lateriflora Convolvulus sepium 



Mentha canadensis Ulmus americana 



This society consists of nine Cornus stolonifera in the sec- 

 tion studied, and occupies an area 20 feet broad. About 10 feet 

 to the west is another Cornus stolonifera far down into the 

 Hibiscus-Typha zone; and about 40 feet still farther west, is a 

 group of 15-18 feet tall Cephalanthus occidentalis which extends 

 through the Hibiscus zone to the water's edge. Just east of the 

 eastern margin of the transect is another group of Cornus with 

 Sambucus canadensis. 



The swamp-shrub association does not exhibit lateral zona- 

 tion, but alternations as it consists of isolated shrub societies of 

 which Cornus stolonifera is the principal species in one and 

 Cephalanthus occidentalis in another. The associated species are 

 grouped closely around the Cornus, most of the herbs form a 

 sparse growth in the shade of the shrubs and Micrampeles and 

 Solanum climb' over them. 



The two bordering associations the marsh-herb on the one 

 side and the forest on the other, merge in the areas between the 

 shrub societies. The presence of seedhng Ulmus, Quercus and 

 Gleditsia in the Hibiscus-Typha society shows clearly that the 

 forest is invading the marsh, and if the higher portion of the mud 

 flat is not again submerged, the shrub zone may never become 

 more complete than it is now ; it may be formed farther down on 

 the shore or it may be entirely replaced by the forest. The 

 incompleteness of the shrub zone is due to the existence of 

 the forest prior to the development of the marsh. 



