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 Nelumbo leaves to the tall Ulmus americana 

 and Quercus palustris. This is well shown in the photograph. 

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



FiG. 29. — View farther west than Fig. 28. Polygonum emersum forms 

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

 map. 



vidual 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. 



