V 



ECOLOGICAL CROSS SECTION OF THE MISSISSIPPI. 179 



studied which presents so great an assortment of species and 

 genera, so luxuriant a plant growth, as does the talus of 

 the Missouri bluffs. The flora combines many of the elements 

 of the plateau forest, and of the ravine in addition to those 

 of the cliff, while at the same time the railroad, which passes 

 at the foot of the bluff, is instrumental in the introduction and 

 distribution of not a few species. The numerous springs and 

 the drainage from the plateau offer a never-failing source of 

 moisture, the amount of which never, except perhaps in the 

 early part of the year, becomes excessive, owing to the slope. 

 The soil is of the richest since in addition to the humus 

 locally formed, a large amount of colluvial soil is annually 

 obtained from the plateau. The exposure being an eastern 

 one, the plants have the benefit of the early morning sun and 

 are protected from the too ardent afternoon rays. All these 

 factors combine to bring about optimum conditions and are 

 largely instrumental in enabling the talus to support a vege- 

 tation without parallel in this region. 



Trees and shrubs are numerous. The most prominent are 

 Admina triloba^ Ceanothus americanus^ Rhamnus carolinianay 

 Aesculus glahray Negundo acerchdes^ Cercis canadensis ^ Fraxinus 

 americanaj several species of Quercus and Populus moni- 

 lifera. Ilex decidua occurs at Wickes only. The undergrowth 

 is composed largely of Celastnis scandenSj Rhus Toxicodendron, 

 Rosa setigera, Rubus ocddentalis and R. villosus. 



While the foregoing species give the general aspect and 

 clothe the lower hill with verdure, the herbaceous plants 

 furnish the brighter colors, especially during the late summer 

 and fall, when yellow is the dominant color. The spring 

 brings with it various Ranunculaceae, such as Anemone 

 virginiana, Ranunculus ahortivus and R. septentrionalis , as 

 well as other low growing species. These include PodophyU 

 lum peltatum, Sanguinaria canadends, Viola palmatay V. pal- 

 mata cucullatay V. Rafinesquiiy Claytonia virginica, Geranium 

 carolinianum and G. maculatum, Trijolium, pratense, T. 

 repenSy Fragaria virginiana^ Potentilla canadends, Chaero- 

 phyllum procumhenSj Phlox divaricata, P. pilosay Hydro- 

 phyllum appendiculatum J H. canadense, and H. virginicum, 

 Lithospermum canescens, with its striking, orange-colored 



./ 



- J 



