ACID, OR 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. 

 \\Yeds 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 FLOURISH ON SOUR SOILS 

 Common name Botanical name 



Sheep sorrel 1 . . . Rumex acetosella 



Paintbrush .... Hieracium aurantiacum 



Daisy . , . . . Bellis perennis 



Horsetail rush 2 . . Equisetum arvense 



Corn spurry 2 . . . Spergula arvensis 



Wood horsetail 2 . . Equisetum syhaticum 



Plantain l . . . . Plantago major 



Goose grass 3 . . . Polygonum aviculare 



1 Knisely, A. L. Acid Soils. Oregon Agr. Exp. Sta., Bui. 

 90, p. 23. 1906. 



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

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



3 Voelcker, J. A. The Woburn Field Experiments. Jour, 

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



