BIG SPRING PRAIRIE. 53 



Hoar-hound); Eupatorium perfoliatum (Boneset); Poten- 

 tilla monspeliensis (Bushy Ciuquefoil); Aster vimineus 

 (Small white Aster). 



The following occur still less frequently: Rosa Car- 

 olina, Asclepias tuberosa, Onagra biennis, Carduus mu- 

 ticus, Iris versicolor, Sambucus canadensis, Urtica gra- 

 cilis. From the cultivated ground the following are the 

 most plentiful: Achillea millefolium (Millfoil or Yar- 

 Tow); Dipsacus silvestris Mill. (Wild Teasel); Oxalis, 

 (two species) Ambrosia artemisiaefolia (Bitterweed, 

 Ragweed); Chenopodium album L. (Lambs-quarters); 

 Amerantus retroflexus L. (Rough Pigweed); Nepeta 

 cataria L. (Catnip); Rumux crispus L- (Curled Dock); 

 Polygonum hydropiper L. (Water-pepper); Polygonum 

 persicaria Iv. (Lady's thumb); Leptilon canadense (L.) 

 Britt. (Horse-weed) and Convolvulus sepium L. (Hedge 

 Bind-weed). In the eastern portion of field, there 

 are a few Crataegus and one specimen of Gleditschia 

 triacanthus. 



The introduced species in this field occur most 

 commonly where there are breaks in the sod or upon 

 the soil thrown from the ditches. A dense sod seems 

 to be an effectual preventative against the encroach- 

 ment of most species of plants. The plants which will 

 gain a foot-hold upon the suitable places are chiefly 

 those which occur on the areas around it to the windward, 

 and under similar ecological conditions of soil, moist- 

 ure, etc. This fact is strikingly illustrated in compar- 

 ing field H, a natural grassy meadow along the western 

 border of prairie, with artificial meadow A in the east- 

 ern portion. Fields F and B are closely allied in phys- 

 ical and chemical characteristics of soil to field A, and 

 the wind is suitable for seed dissemination, in conse- 

 quence, we find many species in common. 



FIELD H. 



This is a natural meadow. It is strikingly differ- 

 ent in physical and chemical characteristics of soil from 



