INTERDUNAL PONDS AND TAMARACK SWAMPS 195 



Chicago area. It is, furthermore, a widely distributed associa- 

 tion found at its best in northern North America and Eurasia 

 covering very wide areas. The sphagnum bogs found as far 



232 



233 



235 236 



FIGS. 231-236: Fig. 231. The sundew, Drosera rotundifolia; Fig. 232. 

 Tickseed, Coreopsis gfandiflora; Fig. 233. Cottony grass, Eriophorum gracile; 

 Fig. 234. Swamp horsetail, Equisetum fluviatile, and section of stalk; Fig. 235. 

 Swamp fern, Aspidium Thelypteris, and under side of one pinnule; Fig. 236. 

 Sphagnum moss. 



south as the Chicago area are isolated areas islands in the midst 

 of the more typical associations. As will be seen in a later chapter 

 they are probably remnants of the vegetation that was quite wide- 

 spread in this region immediately following the glacial period. 



