3o8 wherry: acidity and alkai^inity 



Specific acidities greater than looo are shown only by bog- 

 peat, which supports a characteristic flora of "oxylophytes" 

 or acid-soil plants; for such reactions the term superacid may be 

 used. Some bog-peats, many upland-peats, and other soils also 

 supporting oxylophytes, show values of from looo down to loo; 

 for these the term mediacid seems appropriate. Many ordinary 

 woods soils and field soils are also acid, but to a degree so much 

 smaller that typical oxylophytes do not grow in them; the 

 specific acidities under such conditions range from loo down to. 

 lo, and may be characterized by the well-known term subacid. 

 The slight degree of acidity represented by numbers less than lo, 

 for which minimacid is suggested, and the similar alkalinities up 

 to lo, minimalkaline, are observed in woods and field soils, also 

 associated with certain types of plants; there is no evidence of 

 marked change in flora on passing the neutral point, so such reac- 

 tions may in general be classed as circumneuiral. The soils de- 

 rived from limestone rocks under conditions where the lime is 

 not extensively leached out, and also natural waters rising 

 through calcareous materials, often show a specific alkaUnity of 

 from ID to loo, and for them the term subalkaline, corresponding 

 to that used on the acid side for a similar range, may be used. 

 Medialkaline and superalkaline soils, using these prefixes in the 

 same senses as was done on the acid side, are presumably met 

 with in "alkali" regions where free sodium carbonate occurs. 



It is realized that the division of reactions into groups of equal 

 length in the above manner is a somewhat artificial and arbi- 

 trary procedure. No claim is made, however, that the dividing 

 lines between the groups are actually important critical points, 

 at which the growth of any large number of species ceases. 

 This method of subdivision and nomenclature is merely put 

 forward to fill what is believed to be a real need, namely, for a 

 series of readily understandable and roughly quantitative terms 

 which may be used in the description of the reactions of soils, 

 especially in discussions of plant distribution.^ 



Certain advantages possessed by the proposed methods of 

 stating reactions may now be indicated. The neutral point is 



^ An example of how the method works out in practice will shortly be published 

 elsewhere. • 



