144 SCIENCE PROGRESS 



and " teart" soils lies then in their physical condition. Hence 

 the production of scouring herbage must be determined to a 

 great extent at least by the special texture of the soil. How 

 then does the soil texture affect the physiological properties of 

 the herbage in this manner ? Chemical analysis has not so far 

 succeeded in demonstrating the presence of unusual substances 

 in the herbage to which the scouring might be attributed. 

 The ordinary methods of food analysis are not sufficiently 

 refined to detect such differences in feeding value as these ; 

 but there must necessarily be a difference somewhere in the 

 proximate constituents of grass from good and from scouring 

 fields. It can only be concluded that under the special soil 

 conditions some abnormal constituent is developed in the 

 herbage having a physiological action provocative of scouring ; 

 and further that the texture determines these special soil 

 conditions. 



Some evidence is already forthcoming that modifications of 

 the soil texture remove the conditions giving rise to a scouring 

 herbage. 



In the two investigations here summarised it is evident that 

 important differences in the textures of the respective types of 

 soils undoubtedly exist which were not indicated by the results 

 of the analysis ; and we cannot but draw the conclusion that 

 mechanical analysis according to our present methods is not 

 of the same value in the study of pasture soils as it has proved 

 to be in the case of arable soils. This is probably because 

 of the controlling influence exercised by the organic matter 

 in pasture soils and a place of primary importance must be 

 assigned to this constituent of the soil in determining the type 

 and composition of the herbage. Physical properties which, 

 from analogy with arable soils, might reasonably be inferred 

 from the results of mechanical analysis are, in the case of soils 

 permanently occupied by grass, often masked by the influence 

 of the organic matter present. No doubt the undisturbed con- 

 dition of the surface soil and the consequent slow rate of 

 decay of the humus accounts for this. 



As to the manner in which the action becomes operative 

 we are at present entirely in the dark. Analyses of the herbage 

 by our present methods have led to nothing and it seems 

 probable that before it will be possible to throw much light 

 on this point we shall need to possess more delicate methods 



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