168 ILLINOIS STATE ACADEMY OF SCIENCE 



Denticula, Navicula and Asterionella. The second type 

 is that of the filamentous and attached forms, of which 

 the most abundant species are Spyrogyra, Oedogonium, 

 Oscillatoria, Cladophera, Elodea and Ceratophyllum. 

 The floating leaved aquatics are rather poorly represent- 

 ed, only two species, Lemna minor and Wolffia Colum- 

 biana, being found. 



The vegetation in the swamp is predominated by Ty- 

 pha latifolia, Saggittaria latifolia, and Juncus effusus. 

 The most typical swamp vegetation is in the area east 

 of the pond. The lake was without this stage a year ago 

 because of the permanent lowering of the water two years 

 ago, leaving the plants of this society in conditions such 

 as to make their development impossible. This society 

 developed on the crescent shaped area at the west end 

 exposed by the receding water and on a narrow strip on 

 the steeper slope at the west end. 



Another hydrophyte, water cress (Radicula Nastur- 

 tium acquaticum), is found in great abundance in the 

 spring fed creek into which flows the north outlet from 

 the lake. It is found only above, never below, the point 

 where the lake drainage enters the stream; so we may 

 understand that the water in the lake is very different 

 from spring water. 



The next stage is that of the terrestrial types, which 

 are divided into the lower flood plain group, growing in 

 soil that is saturated continually, and the upper flood 

 plain group, growing in soil that is always moist but not 

 saturated. These names are used because the develop- 

 ment of a pond beyond the aquatic stage is very similar 

 to that of a river flood plain. The lower flood plain 

 society is best illustrated at the outer edge of the low 

 area at the west end of the pond. The most notable 

 species are Polygonum hydropipen (water smart-weed), 

 Centricus carolinianus (sand bur), Xanthium spinosum 

 (cockle bur), Ambrosia trifids (great ragweed), Bidens 

 frendosa (begger tick), Taraxacum officinale (dande- 

 lion), Nepta cataria (catnip), Arctium minus (burdock), 

 Salix alba (white willow), Postinaca stiva (wild parsnip), 

 Oenathera biennis (evening primrose), Carex conjuncta, 

 and Equisetum arvense (horse tail). 



