ECOLOGICAL CEOSS SECTION OF THE MISSISSIPPI. 



183 



later part of the year. On their borders they support a 

 vegetation composed mainly of Umbelliferae and Polygona- 



ccae together with rushes and grasses. Cicuta maculata 

 and Slum cicutae folium are most frequent, as are Poly- 

 gomim HydropipeVj P, hydropiperoides^ P. MiMenhergii and 

 P. Perdcaria. Several species of Carex, Cyperus acumina- 

 tuSj C. erythrorhizos, Dulichium spathaceiim^ Eleocharis acicii- 

 laris, E. ovata, Eriophonim lineatum and Scirpus laciistris^ 

 Alopecurus geniculaiuSj EragrosHs reptans, Glyceria nervata, 

 Leersia oryzoideSj Panicum Crus-galli and Spartina cynosuroides 

 are frequent, as are patches of Typha latifolia. Different 

 species of Sagittaria frequently occupy the major part of 

 the ponds. Here and there Alisma Plantago occurs. While 

 Cephalanthus occidentalisy cither isolated or in groups, is or- 

 dinarily found at every pond, Acer dasycarpimi and Betida 

 nigra may likewise be encountered. Lythraceae-Onagraccae, 

 such as Ammania cocciriea, Rotala ramosior^ and Ludwigia 

 palustrisj are not infrequent. Jussieua repens^ though sel- 

 dom absent, nowhere on the Missouri side attains the truly 

 magnificent development exhibited in the American Bottoms, 

 During the summer Iva ciliata^ Ilysanthes riparia, Mimuhis 

 ringens, Veronica peregrinay Lobelia syphilitica^ Lycopus 

 sinuatus and L. virginicus are always found in the imme- 

 diate vicinity of ponds. Later Aster salicifolius, Coreopsis 

 aristosa and its variety mutica are added. 



THE MISSOURI BOTTOM. 



The dry bottom. 



The dry bottom, on the Missouri side, comprises a strip 

 some twenty to fifty yards wide immediately adjacent to 

 the railroad tracks but situated several feet lower. Trees 

 and shrubs are ordinarily isolated and consist of specimens 

 of Acer dasycarpumj Aesculus glabra, Gleditschia triacanthos, 



Gymnocladus canadensis, Robinia Pseudacacia, Amelanchier 

 canadensis, Prunus serotina, Fraxinus americana, Ulmus fulva, 

 Morus rubra and Betula nigra, with here and there brambles 

 and plants of Vitis dnerea and V, riparia, Rhus Toxicodendron 

 and Tecoma radicans. The more common weeds occur with 

 the greatest frequency, among them Myosurus minimus 



