1912] SHERFF—SKOKIE MARSH 417 
mented or replaced by Polygonum Muhlenbergii, P. hydro pi peroides, 
Veronica Anagallis-aquatica, Radicula aquatica, Sium cicutaefolium, 
Sparganium eurycarpum, Glyceria septentrionalis, Alisma Plantago- 
aquatica, Rumex verticillatus, Callitriche heterophylla, and C. palus- 
tris. As Polygonum hydropiperoides and Sium cicutaefolium are 
among the most abundant stream plants and appear to be dominant, 
we may classify the plants growing in the stream or upon its bed, 
Fic. 2.—Skokie Stream at point west of Braeside, looking north; July 
except along the margins, as the Sium-Polygonum association ; 
using ScHouw’s method of nomenclature (ScHOUW 14, pp. 148- 
150), we shall call this the Sio-polygonetum. On either side of the 
Sio-polygonetum a narrow or sometimes broad girdle* of Nymphaea 
advena and Castalia odorata occurs in many places along the stream. 
Usually these species are accompanied by species characteristic 
of the Sio-polygonetum; but the soil and light conditions present in 
4 The word “girdle” is here equivalent to the “zones” of many recent authors, 
and conforms with the recent proposal of FraHAULT and ScuRrOTER (5), except that it 
is here used for “bands” that are not “concentric.” 
