141 



black mud are iii the progress of formation. The waves throw up the mud 

 in the form of loops and bands, and so form small irregularities in the 

 coast line. An examination of the mud thi'own up or built up in these 

 situations shows it to be composed of small pieces of Scirpus in various 

 stages of decay. Thus the Scirpus furnishes a large amount of material 

 for the building up of new shores. Besides the comminuted and decayed 

 Scirpus there are occasional banks of broken Scirpus stems, not yet de- 

 cayed nor much broken up. piled like windrows up beyond the summer 

 water line. These banlvs are probably piled up during the high water 

 of spring or shoved up by the ice. Upon the soft, black mud banks men- 

 tioned above, there springs a dense growth of annual weeds which forms 

 the advance guard of land vegetation in these regions. 



It may be that the lake plain has for its foimdation decayed Scirpus 

 stems, to which is added turf from the seiiges that today so thickly clothe 

 it.s surface. 



As has been said, long stretches of shore are made up of a lirm. whitish 

 sand. Such stretches are to be found along the Assembly groiinds, north 

 of Chicago Hill piei-, and in the vicinity of the mouth of Clear Creek. This 

 sand is often found floating in lilnis on the surface of th(s water near 

 shore. At the mouths of the creeks, banks or deltas of white sand are 

 built up and these project above the surface of the water when the lake 

 is low, and form islands. At other places it can not be said detiniti'ly that 

 either erosion or sedimentation is taking place. Gently lapping waves will 

 pile up a narrow ridge of sand just at the edge of the Avater. but high, 

 strong waves will wash them down again. During active wave motion the 

 advance of the waves will move particles of sand shoreward, while the 

 back flow will move them back about the same distance. 

 I Frequently on the sandy banks, perhaps eA^ery where in such places 

 Avhere not interfered with, the three-cornered rush Scirpus americanus, 

 groAA's out and forni.s the adA'ance guard of vegetation. 



THE FLORA OF THE LAKE SHORE is not essentially different in 

 species from that of the shallow ponds adjacent to the lake, especially the 

 large pond on the southern shore. The only difference is that the plants 

 in that pond (bulrush, cat-tail> spatterdock. pickerel-weed and arroAvhead) 

 form large patches, as they haA^e here a broad region of shallow water and 

 congenial soil. Along the lake shore the plants, all except the bulrush, 

 form comparatively narroAy belts. i\[ost of the bulrushes {Scirpvs lacustris) 

 in the ponds outside of the lake are light in color and soft in texture •(there 

 9— .Academy of Science. 



