AX ARTIFICIAL PRAIRIE 



37 



found on both the prairie strips and in the bordering forest ; the 

 two remaining species, Gentiana flavida and Silene stellata, also 

 occur sometimes in the woods of this general region but were not 

 observed in the vicinity of the road. The greater part of the list, 

 66 species, is made up of characteristic prairie plants which are 

 wholly wanting in the adjoining forest, and which could not 

 have been a part of the flora which originally covered the road- 

 strip. Very few weeds were introduced with this prairie flora 

 and these are largely restricted to the immediate border of the 

 road-bed. Some years ago small portions of the roadside were 

 not cleared for some time and the forest flora rapidly advanced, 

 producing bordering thickets. The vanguard of such an advance 

 usually consists of Corylus americana, Bhus glabra, Populus 

 tremuloides, Quercus macrocarpa, Crataegus Margaretta, Rubus 

 aUeglieniensis, and other hardy trees and shrubs, among which 

 the smaller herbs soon appear. Individual specimens of these 

 trees and shrubs are scattered along the prairie border in some 

 places, but they are kept in check by the periodic clearing of the 

 roadside. 



A comparison of the flora of this prairie strip with that of the 

 adjoining forest brings out in a striking manner the difference 

 between these floras. An examination of the forest list shows 86 

 species of vascular plants of which 6 are pteridophytes, and 17 

 monocotyledones. The dicotyledonous plants are almost equally 

 divided between herbs and woody plants. Of this list 9 species 

 (those marked *) also occur on the prairie. Of the latter number 

 5 were here not found on the prairie border but occur on prairies 

 elsewhere. The greater part of the list, 77 species, is made up of 

 species which are characteristic of the forest and undoubtedly 

 represent the bulk of the flora which originally covered the road- 

 strip. 



The source of the introduced prairie flora is probably to be 

 sought in the prairie which originally covered the territory 

 south of the forest here discussed, the remnants of the flora of 

 which are still preserved along the Chicago, Rock Island and 

 Pacific Railway, and elsewhere. Another prairie area is located 

 on the bottomlands north of the river, but this probably con- 

 tributed very little to the introduced flora of the road-strip. 



The manner of introduction is suggested by a review of the 

 habitual methods of seed dispersal of the introduced species. Of 



