Feb., 1913.] Characteristic Plants of a Typical Prairie. 67 



tion on the young flood-plains of a forested region like Ohio. They 

 owe their existence to the presence of the river and not to the 

 climatic conditions. 



The prairie fire, although not the cause of the prairies, had, 

 nevertheless, a profound eftect on their vegetation. When the 

 fires swept over the prairie in the spring, it burned up everything 

 down to the ground, and perennial herbs and shrubs had each 

 year to meet anew the competition above ground of the all-con- 

 quering grasses. Frequently the fires occurred in the fall and 

 thus the soil was exposed, without covering, dming the entire 

 winter to dryness, wind and cold. Since the fires have ceased 

 even the patches of prairie still remaining are undergoing a rapid 

 and remarkable change in vegetation. The change in the relative 

 abundance of certain species is no less interesting than the arrival 

 of new forms from other regions. 



After the characteristic grasses, the most prominent members 

 of the prairie vegetation are a number of shrubs and perennial 

 geophilous herbs. The latter are usually crownformers, often 

 with exceedingly long taproots. When one sees such plants 

 exposed in the banks of a stream or an arroyo, one realizes what a 

 large part of the vegetation is underground in summer as well 

 as in winter. 



The woody or semi-woody species are few in number, though 

 several are among the characteristic prairie plants. The most 

 important one in the region under consideration is the shoe-string, 

 Amorpha canescens Pursh, which is a low shrub a foot or two in 

 height. Others are, Rosa arkansana Port., Arkansas Rose, 

 Meriolix serrulata (Nutt.) Walp., Tooth-leaf Evening-primrose, 

 and Morongia uncinata (Willd.) Britt., Sensitive-brier. The 

 latter is only slightly woody. In the ravines, Amorpha finiticosa 

 L., false indigo, is especially abundant on the banks of ponds. 

 Salix fluviatilis Nutt., Sandbar willow, grows in small dense 

 thickets in moist ravines and is occasionally present on banks and 

 hillsides. In such situations, however, the shrub is always 

 very small. 



Very few seedless plants thrive on a typical prairie. There are 

 no ferns on the prairie proper but Wocdsia obtusa (Spreng.) Torr. 

 grows on moist sandstone cliffs along with several species of mosses, 

 liverworts, and lichens. Equisetum kansanum Schaff. occurs on 

 clayey banks and slopes and Marsilea vestita H. & G. grows 

 occasionally in buffalo-wallows in low places. The Marsilea 

 seems to be near its eastern limit and is properly a plant of the 

 plains. There are very few mosses but some small ground-loving 

 lichens occur especially on the hills and Nostoc commune Vauch. 

 is abundant on the banks of ravines. The giant puft'ball, Lyco- 

 perdon gigantemn Batsch., often occurs in large numbers and in 

 suitable seasons various other species of puff balls, toadstools and 

 stink-horns make their appearance. 



