36 



and (ii.) an abnormally low variation ascribable to defective pro- 

 cedure in the preparation of the medium. Application of the same 

 tests to other extensive series of bacterial counts showed that a 

 similar approach to theoretical accuracy, though rare, had been 

 obtained by Breed and Stocking- in counts of B. coli in milk. It 

 should be emphasised that all cases of departure from the theoretical 

 law of distribution, which have been investigated, are associated 

 with large systematic errors in the counts; for this reason simple 

 tests are presented by which such deviations from the theoretical 

 accuracy of the method can be detected. 



ACCURACY OF APHIS COUNTS. 



XV. R. A. FiSHEK. ''Appendix to 'Biological Studies of 



Appiis Rumicis,' by J. Davidson." Annals of Applied 

 Biology, 1922. Vol. IX. pp. 142-145. 



A special method was developed for determining the accuracy 

 of Dr. Davidson's counts on Aphids ; by this means it was possible 

 to show that the 19 varieties of bean tested could be assigned to 

 only six degrees of susceptibility to aphis infestation. 



MANUKIAL response OF POTATO VARIETIES. 



XVI. R. A. Fisher and W. A. Mackenzie. "The Manurial 



Response of Potato Varieties." Journal of Agricul- 

 tural Science, 1923. Vol. XIII. pp. 311-320. 



In an experiment carried out at Rothamsted (1922), twelve 

 potato varieties were each tested with six different manurial treat- 

 ments, each test being triplicated. Consequently it was possible 

 to test a question upon which very little information has hitherto 

 been available, namely, whether different varieties respond alike to 

 manurial treatment. It is impossible to generalise from a single 

 test of a single species, and it has seemed to the authors of more 

 importance to call attention to (i.) the kind of data required for 

 such an enquiry, and (ii.) the type of statistical treatment needed to 

 elicit an answer, than to emphasise the fact that no significant 

 differences are observable in the manurial response, although the 

 varieties differed much among themselves in yield, and the different 

 treatments also resulted in large differences in yield. 



SOIL ORGANISMS. 



XVII. E. J. Russell, "l.es Micro-Orgaiiismes du Sol dans 



leurs rapports avec la croissance des plantes. Posi- 

 tion actiielle du prohleme." Ann. de la Sci. Agro- 

 monique, 1921. pp. 49-67. 



A review of the present position of our knowledge on this 

 subject. 



ALG/E. 



XVIII. B. Muriel Bristol and Harold J. Page. "A Critical 



Enquiry into the Alleged Fixation of Atmospheric 

 Nitrogen." Annals of Applied Biology, 1923. 

 Vol. X. pp. 1-30. 



