hankinson] 



ANIMAL LIFE IN PRAIRIE PONDS 



237 



ponds, compared with those in the dry, level, monotonous surround- 

 ing country, that the discovery of one of these habitats by a prairie 

 naturalist, gives him a pleasure that must be something like that 

 of a desert traveller on finding an oasis. 



In the prairie region just north of Charleston, Illinois, there are 

 a few of these ponds. The largest covers three or four acres. The 

 vegetation is abundant in them and has the usual zonal arrange- 

 ment found in ponds. Some cottonwoods grow in the center in all 



Fig. 3. Portion of a Prairie Pond, showing details of the Grass Zone 



cases. Around these, is a more or less complete zone of willows, 

 and then comes a region of marsh plants, which is only well-devel- 

 oped in the larger ponds, where it almost completely surrounds the 

 willow growth. A thick, triangled-stemed, and flat -leaved rush 

 {Scirpus rohustus) is the chief plant here; but associated with it 

 are some sedges and smartweeds and a few other plants, that thrive 

 when partly submerged. A broad, distinct, zone of low herbs, 

 chiefly grass, adjoins this and forms the outermost region of the 

 pond. Patches of low button bushes {Cephalanthus) help to form 

 a border in a few cases. In the early spring, water stands over 

 most of the region, and it is ordinarily shallow enough and over a 



