153 



Cladium mariscoides grows in several small patches at the edge of the 

 lake, mixed in with the Scirpvs. Eleocharis palustris grows in the lake 

 rather scantily in two places, one just a little north of Chicago Hill pier, 

 at the beginning of the Scirpvs patch, and the other a little south of Yai'- 

 nelle's landing. Eleocharis interstincta and E. mutata form each two small 

 patches along the southwestern shore of the lake and at Yarnelle's landing. 

 There were only a few duckweeds (Spirodela) found in the lake proper. 

 This was along the southern edge, where it was shady and calm. 



GENERAL RELATIONS.— The plants on the shore, especially those 

 which grow out upon newly-made soil, probably have a good deal of influ- 

 ence in binding the shore together, and assist in the encroachments of the 

 land upon the lake. This influence, however, is difficult to measure or 

 express in definite terms, for it seems ii'regulai* and uncertain, as erosion 

 goes on quite rapidly even where tliere are forests on shore, wherever the 

 wind has full sweep. Small trees are uprooted and fall, and in some places 

 stumps are found in the bottom of the lake near shore. 



THE PLANTS IN THE WATER, especially the Scirpus, form a large 

 amount of material for the building up of new shore. They also break the 

 influence of the waves against the shore. At times, when the surface of 

 the lake was quite rough, the water above a large patch of water weeds, 

 particularly Potamogeton amplifoUvs, was often noted to be perfectly calm. 

 The large submersed leaves of the latter plant are very effective in catch- 

 ing the moving molecules of water, retarding their motion, and so prevent- 

 ing waves. 



The larger plants in the lake bear certain relations to the plankton. 

 Among the Scirpi, the Glathrocystis scum is abundant almost any time 

 during the latter part of the summer. Here we have a marked influence 

 on the vertical distribution of the plankton. On the afternoon of August 

 21, 1900, a thickish coating of clathrocystis was noted among the bul- 

 rushes near the shore, and during the night the lapping waves piled it up 

 in a narrow streak along the water line. 



The stems of the water plants furnish lodgment for many aquatic 

 plants and animals. Fresh water sponges grow abundantly upon the 

 Scirpus stems. 



A peculiarity of a species of Rivularia may be noted in this connection. 

 It frequently grows quite abundantly attached in small hemispheric masses 

 to stems and leaves of water plants. I have never seen it floating in 

 Eagle Lake at all, and Dr. Howe, who has worked pai'ticularly with the 



