42 THE PLANT SOCIETIES OF 



geton (Pondweed ),^a««w<:«/«j-a^2/a///w (White buttercup), Brasenia,Ne- 

 lumbo (Lotus), Myriophyllum (Water milfoil), Ceratophyllum (Horn- 

 wort), Elodea(Waterweed),Vallisneria(Tape'grass), and Naias. This rank 

 growth of vegetation fills the lake up rapidly, since the currents are not 



sufficient to carfy off the plant remains. There is a rapid advance of 

 marginal plants upon the lake, a phenomenon that is shown inyf^. 22, 



FlG.24.— Typical grass prairie near Pullman. This prairie has been reclaimed naturally 

 from Lake Calumet, and has passed through bulrush and sedge stages. 



where the scattered bulrushes {Scirpus laciistris) are seen to be soon fol- 

 lowed by a dense bulrush society. With or soon after the bulrushes 

 are a number of marginal plants, Especially Typha latifolia (Cattail), 

 Pontederia cordata (Pickerel weed), Sparganium eurycarpum, Sagittaria 

 variabilis and S. heterophylla (Arrowheads), Zizania aquatica (Wild rice), 

 Phragmites communis (Reed), Acorus Calamus (Sweet flag), and Erio- 

 phorum cyperinum. Fig. 2j shows a stage in which a lake has been all 

 but destroyed by a rank bulrush vegetation. 



C. The prairie. — Sedges encroach rapidly upon the bulrushes as the 

 new soil becomes raised more and more above the lake, and grasses in 

 turn encroach upon the sedges, forming a prairie. Fig. 24. shows an 

 expanse of grassy prairie which has developed through these successive 



