COLLINS; INTOLERANCE TO SELF-FERTILIZATION 309 



clearly marked by the figure o; the exponents of the H and OH 

 ions present in a given solution differ only in sign, and solutions 

 of equivalent acidity and alkalinity are described by numerically 

 identical terms, which is not the case in the usual methods. 

 But the most desirable feature appears to the writer to be the 

 ease with which the relative magnitudes of reactions under com- 

 parison can be appreciated when the numerical specific acidities 

 and alkalinities are used. For example, in a recent study of the 

 occurrence of azotobacter in cranberry soils^ it was found that 

 untreated soils had ?„ = 54 to 5.6, and limed soils 6.2 to 6.4. 

 With this method of statement it is not apparent, without stop- 

 ping to calculate it out, in what direction the reaction has been 

 altered or how extensive the change has been. If the same data 

 are stated by the proposed chemical potential method, however, 

 Xh = 1.6 to 1.4 and 0.8 to 0.6 respectively; and when 10 is 

 raised to these powers the corresponding numerical specific 

 acidities are 40 to 25, and 6 to 4, showing directly and clearly 

 that liming has reduced the acidity to about Ve of its original 

 amount. 



In conclusion, it may be remarked that the proposed methods 

 of describing reactions are by no means adapted only to work 

 with soils; they may prove useful in other fields as well. It 

 may be urged especially that the readiness with which the numer- 

 ical specific acidities and alkalinities can be understood by workers 

 in nonmathematical sciences should lead to favorable consider- 

 iation of this method whenever results obtained by physical- 

 chemical measurement are to be applied in other fields. 



BOTANY. — Intolerance of maize to self-fertilization. G. N. 

 Collins, Bureau of Plant Industry. 



Of the important cultivated crop plants maize is perhaps the 

 least tolerant of self-fertilization. Only one strain among hun- 

 dreds that have been tested has yet been discovered, the vigor 

 of which is not reduced by even a single generation of self-fer- 

 tilization. Many strains that have been under investigation 



* Gainey, Science 48: 654. 1918. 



