ECOLOGICAL CROSS SECTION OF THE MISSISSIPPI. 



169 



sinkholes consists of grasses and sedges, chiefly Cyperus 

 acuminatus and C. erythrorhizos , Dulichium spathaceum, 

 Eleocharis adcvlaris, Sdrpus lacustris, Glyceria nervata and 

 Leersia oryzoides. Ordinarily the wet sinkholes in the field 

 are of small depth, the soil from the surrounding slopes being 

 washed down in great quantities, not being retained by roots, 

 etc, as in the case of a wooded pond. Hence the majority 

 are sufficiently shallow to accommodate species of Sagittaria, 



especially S. variabilis. 



here 



wooded ponds or in the bodies of water 



Bottom 



Shaded hillsides. 



The well drained, shaded hillsides offer 

 tions to the plants of the region studied. I 

 possess excellent drainage but soil is continually washed 



optimum 



do 



from the higher slopes while at the same time 

 Y formed is, for the greater part at least, reta: 

 while still dominant, are not arranged as de 



The 



dry, open wood, and shrubs 



The species 



named 



(Q 



coccinea 



Q. imbricaria, Q 



Q. nigra, Q. Schneckii, Q. stellata) , hut they are mtcrspersed 

 with numerous specimens of Ulmus fulva. Cercis canadensis 

 is prominent. The principal shrubs are Ptelea trifoliata, 

 Euonymus atropurpureus , Ceanothus americanus and Rhamnus 

 lanceolata, with an undergrowth 



smaller shrubs 



as 



Rhus glabra, Rhus canadensis and Symphoricarpus vulgaris. 

 Ampelopsis quinquefolia climbs the larger stems and Vitis 

 riparia and Rhus Toxicodendron twine among the bushes. 



most 



Hydrastis canadensis, Delphinium tricorne, Podophyllum pelta- 

 tum, Viola palmata and V. polniata cucullata, Geranium 

 maculatum, Gmm album, Heuchera americana, Sanicula 



ilandica, Polygonatum giganteum and Smiladna race- 



mar 



most 



Trillium re- 



curvatum and T. sessile are not infrequent. Claytonia vir- 

 ginica, wherever an open space occurs, blooms in profusion 

 during March and April. It is to be noted that the blooming 



