ACID, on SOUR, SOILS 383 



of vegetation and determines to a large degree its nature. 

 The flora undergoes a considerable variation as a soil 

 changes from a basic to a sour condition. This is because 

 some plants are injured to a greater extent than are others 

 by the conditions that accompany an acid reaction of the 

 soil. Some higher plants really grow better on a sour 

 soil than they do on an alkaline one, but these form only 

 a minority of the plants of agricultural importance. 

 Weeds that abound and appear to flourish on acid soils 

 may do so either because they grow better on sour soil 

 than on basic, or because other vegetation growing on 

 the soil does not thrive and therefore the dominant weeds 

 of the region have less competition than they otherwise 

 would have. There are certain weeds that may be taken 

 to indicate a sour soil when present in large numbers. 

 Some of these are found in one part of the country and 

 some in another : — 



Weeds that FLoirEisH on* Sour Soils 



Common name Botanical name 



Sheep sorrel ^ . . . Rumex acetosella 



Paintbrush .... Hieracmm anrantiacum 



Daisy Bellis perennis 



Horsetail rush ^ . . Equisetum arvense 



Corn spurry ^ . . . Spergula anensis 



Wood horsetail ^ . . Equisetum syhaticum 



Plantain ^ . . . . Plantago major 



Goose grass ^ . . . Polygonum amculare 



^Knisely, A, L. Acid Soils. Oregon Agr. Exp. Sta., BuL 

 90, p. 23. 1906. 



2 Whitson, A. R., and Weir, W. W. Soil Acidity and Liming. 

 Wisconsin Agr. Exp. Sta., BuL 230, pp. 7-11. 1913. 



^ Voeleker, J. A. The Wobnrn Field Experiments. Jour. 

 , Royal Agr. Soe. England, Vol. 69, pp. 337-357, 1908. 



