86 



Proceedings of the Ohio State Academy of Science. 



tion and layering (etagen) are strikingly shown. There is a 

 marked increase in elevation from one lateral zone to another, 

 from the floating Xelumho leaves to the tall Ulmus americana 

 and Quercus palustris. Tliis is well shown in the ])h()tograph. 

 (Fig. 28.) There is a poor development of etagen in the indi- 



FiG. 29. — View farther west than Fig. 28. Poh-gonum emersum forms 

 the outermost zone, then follow zones or societies 2, 3, 4, 5, 6 and 7 of 

 map. 



vidua! associations. In some there are the dominant plants and 

 then the ground cover, in others a weak, irregular growth of 

 taller herb's, while in the forest, the shrubs have either been cut 

 or are young plants, and the vines generally trail over the ground. 



