184 OUTLINES OF BACTERIOLOGY 



to produce satisfactory nodules, because the culture of bacteria that 

 was used was not virulent enough. The want of virulence is due to 

 the fact that the species has been grown for several generations in 

 an artificial medium, and that kind of growth has caused it to change 

 its properties. The pure cultures of this bacillus called " Nitragin " 

 which have appeared on the market have-not until recently been an 

 unqualified success, owing to want of appreciation of the selective 

 nature of each variety of Bac. radicicola, beans, for instance, being 

 inoculated with a variety taken from peas, and so on. Mention must 

 also be made of another disadvantage which, like the others, has been 

 overcome. In cultivated soils the seed in swelling, previous to germina- 

 tion, appears to be able to secrete a substance which tends to prevent 

 the formation of nodules. This difficulty was overcome by adding to 

 the solution containing the bacteria 1-2 per cent, of grape sugar and 

 peptone. 



When all these factors are taken into consideration, success has 

 almost invariably resulted. In the cultures sent out, with careful 

 instructions, from the Botanical Laboratory of King's College, London, 

 over 80 per cent, of the experiments were successful, and Prof. 

 Bottomley reports that he was able to grow a fine crop of Mexican 

 beans on volcanic ash by simply adding culture solution to the ash. 

 A couple of examples will be sufficient to indicate the gain derived 

 from scientific inoculation. Tares were grown in sterilised soil. One 

 set of pots received the necessary amount of nitrate of soda ; another 

 set, receiving no nitrate of soda, was inoculated with these bacteria. 

 At the end of the season analysis gave the following results : 



PERCENTAGE OF NITROGEN. 



Tares manured with nitrate of soda, - 1'92 



Tares inoculated,- - 3 07 



In Kilmarnock, field experiments with lucerne resulted as follows : 



PERCENTAGE OF NITROGEN. 



Section A, no nitrogenous manure, - - 3 '41 



B, nitrate of soda added, 3 '1 5 



,, C, inoculated, - - 4*04 



