April, 1908.] 
The Vegetation of Cedar Point. 
3 l 3 
The Lower Beach—The Chlamydomonas Formation. 
Following in part Cowles’ classification 12 of the beach habitats, 
there may be distinguished, first, the Lower Beach, 13 comprising 
that part of the beach washed by the waves of ordinary summer 
storms and thus, chiefly by reason of the mechanical violence of 
the waves and the instability of the sub-stratum, practically 
devoid of plant life. However, as Cowles noted along the lower 
beach of Lake Michigan and as the writer found also on the 
Lower Beach of Presque Isle, a species of Chlamydomonas , a one- 
celled motile alga, occasionally occurs so abundantly in the sand 
as to cause a distinctly green coloration These plants are per¬ 
haps more correctly to be regarded as migrants from the waters 
of the Lake, but, being so abundant in certain wet periods and 
being also the only plant found commonly in the habitat, we 
have termed the formation the Chlamydomonas Formation. 
The Drift Beach—The Cakile-Xanthium Formation. 
Extending from the upper limit of the waves of ordinary 
summer storms, i. e., the upper edge of the Lower Beach, up to 
the upper limit of the waves of severe winter storms, there is a 
zone which may be termed the Drift Beach, 14 which is character¬ 
ized ordinarily by freedom from the violence of the waves of 
summer storms but is subjected to severe mechanical action of 
the waves of winter storms, at which time there is usually left a 
line of driftwood which marks, through the following season, 
the upper extent of the wave action. 
The habitat as thus characterized is inhabited by a vegetation 
composed of such annuals as can endure the summer environ¬ 
ment, the seeds having been left in their present position by 
wave action. Perennials and biennials are, of course, barred 
from this habitat by the destructive effects of wave action during 
the winter. The habitat presents above the surface of the 
sand conditions of excessive insolation, great and often very 
sudden extremes of temperature, great fluctuation in the water 
content of the air, and, also, high winds, and is thus distinctlv 
xerophytic. The edaphic conditions are, however, distinctlv 
hydrophytic below the surface layer of sand so that the habitat 
may, as a whole, be designated as dissophytic. 15 The vegetation 
12. Cowles, H. C. The Ecological Relations of the Vegetation of the 
Sand Dunes of Lake Michigan. Bot. Gaz. 27 : 95-117, 167-202, 281-303, 
and 361-391. Feb., Mar., Apr., and May, 1899. 
13. Cowles, H. C. 1. c. Bot. Gaz. 27 : 114-117. 
14. MacMillan’s “Mid-strand” (Lake of the Woods); Schimper’s 
“Mid-shore”; Cowles’ “Middle Beach” (Lake Michigan); Ganong’s 
“New Beach” (Miscou Island); are all synonyms for the habitat here 
designated as the Drift Beach. 
15. See Clements—Research Methods in Ecology. 
