277 



The Jitncus balficiis lifioralis itself possesses this tendency, but to 

 a less marked degree. The presence of the Scirpns is conclusive 

 proof that wet sand is close to the surface. 



UST OF THE SPECIES OP THE J UNCUS BALTlCUS LITTORAETS 



ASSOCIATION 



Dominant Species 

 Junciis balticits littoralis 



Relic Species 

 Triglochin palusfris 

 Cakile edentiila 



Invading Species 

 Potcntilla anscrina 

 Salix syrticola 

 Populus deltoidcs 



Cycloloiiia afriflici folium 



Ely inns canadensis 

 Scirpns anicricanns 



In addition to the part that the Juncns plays in building up the 

 beach, it has an important role in retarding the storm waves in their 

 attack on the shore-line between Kenosha and Winthrop Harbor. Its 

 efforts are only partially successful as Figure i, Plate XLVI, illus- 

 trates. The relic dune* (A) in the center of the figure and the two 

 at the left, mark the limits of the grassy sand plain in 1905. This 

 plain is usually separated from the lake by a very dense growth of 

 Juncns balticus littoralis. The width of this Juncns association is from 

 one to three meters. It is separated from the grassy plain by a narrow 

 tension zone of Potcntilla anscrina. The interwoven mass of rhizomes 

 of the Juncns protects the sand from sliding. As a result there is nor- 

 mally a perpendicular bluff of i.o to 1.4 meters' elevation at the lake. 

 Repeated buffetings of the lake wear through the Juncns in spots. 

 This affords an opening to the grassy plain behind, with which vio- 

 lent waves make short work. The limit of the wave action is due to 

 the loss of power to move sand after the waves have proceeded over 

 a stretch of beach. The retreating waves carry back with them sand 

 from the rear of the Ju)icns. After about four years of such action 

 the beach line has the appearance shown in Figure i, Plate XLVI. In 

 the center of the figure is a relic dune. Its elevation above the water 

 is the same as that of the grassy plain in the foreground. This is il- 

 lustrated by Figure 2, Plate XLV. The sides of these relic dunes 



*Gates, F. C. Relic Dunes, A Life History. Trans. 111. Acad. Sci., Vol. Ill, 

 1910, pp. 110-116. 



