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, 2 
Cowles at the southern end of Lake Michigan, 3 Ganong at the 
Miscou Beach, 4 and Kearney at the Great Dismal Swamp, 5 and 
at Ocracoke Island. 6 
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 facies. 
The facies may appear separately from each other, each having 
a definite association of accompanying species, and where this 
happens the facies tlms 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 : 949-1023. 1897. 
3. Cowles, H. C. The Ecological Relations of the Vegetation of the 
Sand Dunes of Lake Michigan. Bot. Gaz 27 : 95-117, 1G7-202, 281-303, 
and 361-391. Feb., Mar., Apr., and May, 1899. 
Also the Physiographic Ecology of Chicago and Vicinity. Bot. Gaz. 
31 : 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. 1906. 
5. Kearney, T. H. A Report on a Botanical Survey of the Dismal 
Swamp Region. Contr. Nat. Herb. 5 : 367-395. 1901. 
6. Kearney, T. H. The Plant Covering of Ocracoke Island. Contr. 
Nat. Herb. 5 : 275-284. 1900. 
