April, 1908.] The Vegetation of Cedar Point. 297 



f — The Ce phalanthus-Cornus Thicket Formation, 

 g' — The Rhus hirta Thicket Formation, 

 h — The Ulmus-Acer Forest Formation. 



(The Anomalous Ailanthus Forest Formation). 



THE COTTONWOOD B AR-RIDGE-THICKET-FOREST SUCCESSION. 



As Prof. Moseley has so well shown, the terminal portion of 

 Cedar Point, termed the Ridge Section, consists mainly of a series 

 of sand ridges initiated by northeast gales during times of high 

 water in Lake Erie, and subsequently built up to their present 

 dimensions by the combined action of wind and vegetation in 

 accumulating the loose beach sand. The approximate dates of 

 formation of the ridges are shown to run consecutively from about 

 1-129 A. D. for the oldest ridge, on the Bay side of the peninsula, 

 to 1899 for the youngest ridge along the Lake front. 



Beginning, therefore, with the present Lake Erie beach of 

 the Ridge Section, the vegetation may be discussed from the 

 developmental standpoint from the youngest to the older stages 

 of the succession, the various stages being found in connection 

 with similar physiographic units (sand ridges and intervening 

 depressions) of consecutively older formation. 



During a northeast gale, with high water in the Lake, the 

 loose beach sand may be piled up into a bar which, upon the sub- 

 sidence of the waves, will be left more or less permanently above 

 the ordinary water level. Behind this bar there will be a more 

 or less completely segregated lagoon. Into such a beach lagoon 

 there will be blown during late spring many willow and cotton- 

 wood disseminules, which, floating upon the surface of the water, 

 will soon be deposited and buried in the loose, wet sand which 

 rapidly accumulates around the banks of the newly formed 

 lagoon. Here the disseminules will sprout and the lagoon will 

 soon be bordered by a zone of little cottonwoods and willows. 

 The lagoon may be so narrow as to be completely filled up by 

 the drifting sand before other vegetation may be able to estab- 

 hsh itself, or, if the lagoon be wider, other vegetation may become 

 estabhshed only to be later buried under the sand and killed. 

 In either case, however, a sand rigde has been initiated by the 

 establishment of the zone of cottonwoods and willows. 



With the growth of the cottonwoods and willows there is 

 ofifered an obstruction to the drifting sand, the height of the 

 obstruction by its continued vertical growth tending to build 

 the ridge ever higher. Cottonwoods will continue to grow 

 vigorously under such conditions, providing the tops of the 

 plants are not entirely buried. On Presque Isle the writer found 

 cottonwoods buried to a depth of nearly 30 feet and still vigor- 

 ously growing. As the lower branches of the tree become buried 

 in the sand they die, although for a long time serving the purpose 



