292 The Ohio Naturalist. [Vol. VIII, No. 6, 



The shores of ponds, lakes, and oceans have been the subject 

 of ecological studies to a greater extent than has any other 

 physiographic region. This is, no doubt, due to the concentra- 

 tion in a small space of many different plant formations with the 

 developmental stages exceptionally well defined. Studies of 

 this sort of particular interest with respect to the ecology of 

 Cedar Point, being physiographically quite similar as to the areas 

 embraced, are those of MacMillan at the Lake of the Woods," 

 Cowles at the southern end of Lake Michigan,^ Ganong at the 

 Miscou Beach,'* and Kearney at the Great Dismal Swamp,-'' and 

 at Ocracoke Island." 



As referred to in the present article an association of species 

 occupying a definite, more or less homogeneous unit of ecological 

 environment (habitat), is termed an ecological plant formation. 

 The formation is the unit of vegetation and is always character- 

 ized by one or more dominant species which are termed the fades. 

 The facies may appear separately from each other, each having 

 a definite association of accompanying species, and where this 

 happens the facies thus characterize as many different consocies. 

 Certain species in the formation may become very conspicuous 

 at certain periods in the season (aspects), such species being 

 termed principal species and the associations which they thus 

 characterize, societies. The aggregation of the common descend- 

 ants of a plant constitutes an ecological family and the aggrega- 

 tion of several families an ecological community. 



All plant formations bring about reactions of various kinds 

 in the habitat, — removal of plant foods, accumulation of vege- 

 table debris, cutting off the light, etc., — which usually result in 

 making the habitat less suitable to the resident species but better 

 suited to other species which, by invasion of the altered habitat, 

 may eventually occupy it to the complete exclusion of the species 

 of the original formation. Invasion consists (first) of migration, 

 by which is meant the entrance into the habitat of disseminules 

 of various sorts (seeds, spores, vegetative shoots, etc.), and 

 (second) of ecesis, by which is meant the germination, growth, 

 and establishment of the migrant disseminule. 



2. MacMillan, Conway. Observations on the Distribution of Plants 

 along Shore of Lake of the Woods. Minnesota Botanical Studies. Geol. 

 and Nat. Hist. Survey Minn. Bulletin 9 ; 949-102:1 1897. 



3. Cowles, H. C. The Ecological Relations of the Vegetation of the 

 Sand Dunes of Lake Michigan. Bot. Gaz. 27 : 95-117, 167-202, 2Sl-;i():i 

 and 3G1-391. Feb., Mar., Apr., and May, 1899. 



Also the Physiographic Ecology of Chicago and Vicinity. Bot. Gaz. 

 81 : 73-108, 145-182. Feb. and Mar., 1901. 



4. Ganong, W. F. The Nascent Forest of the Miscou Beach Plain. 

 Bot. Gaz. 42 : 85-87. 1900. 



5. Kearne3^ T. H. A Report on a Botanical Survey of the Dismal 

 vSwamp Region. Contr. Nat. Herb. 5 : 3G7-395. 1901. 



6. Kearney, T. H. The Plant Covering of Ocracoke Island. Contr. 

 Nat. Herb. 5 : 275-284. 1900, 



