59 6 



ZONES AND REGIONS [Pt. Ill, Sect. II 



conspicuous plants are, however, Asclepias Jamesii and Cnicus ochrocentrus, 

 which are one or two feet high. 



Fringing-forests are developed along water-courses that never or rarely overflow 

 their banks (Fig. 331). The dominating trees are : Asimina triloba, Tilia americana, 

 Acer dasycarpum, Negundo aceroides, Cercis canadensis, Gymnocladus canadensis, 

 Gleditschia triacanthos, Ulmus americana, Celtis occidentalis, Morus rubra, Platanus 

 occidentalis, Juglans nigra, Carya olivaeformis, C. sulcata, C. amara, Quercus macro- 

 carpa, Q. palustris, Salix amygdaloides, S. nigra, Populus monilifera. The shrubs 

 (and lianes) are : Menispermum canadense, Zanthoxylum americanum, Vitis cinerea, 

 V. cordifolia, Aesculus arguta, Staphylea trifolia, Ribes gracile, Sambucus cana- 

 densis, Symphoricarpos vulgaris, Smilax hispida. 



Fig. 334. Natural prairie (prairie-grass formation), Lincoln, Nebraska. 375 meters above sea- 

 level. March 19, 1898. Sporobolus asperifolius, Koeleria cristata, Panicnm Scribnerianum. From 

 a photograph by Bessey. 



Pound and Clements ] have recently given an excellent description of the 

 oecology of the State of Nebraska (Figs. 334, 335), the greater part of which 

 belongs to the original prairie district. The grassland covers wide un- 

 dulating tracts and, in the deeper and moister places, assumes a character 

 more meadow-like, and on the ridges more steppe-like. Moreover, the 

 latter is more xerophilous on clay soil {buffalo-grass formation) than on 

 loam {prairie-grass formation). 



1 Pound and Clements, op. cit., p. 348. 



