496 CONTRIBUTIONS TO OUK KNOWLKDGK OP SOIL-FERTILITY, ii. 



EXPKKIMENT ii. 



Quantity of air- 

 dried soil added to 

 500 c.c. then 2 CO. 

 to 98 CO. 



5 grin. 



25 grni. 



50 ^rin. 



125 grm. 



5 gnn. 



Rhizohium- 



colonies 

 on plates. 



Rkizobia in 1 grm. of dry soil. 



Reaction^ 



+ 0-2 



0-2 



9 

 1 



7- 







4 



3 



1 

 2 





 1 



1,870,000 



t41,000 



140,000 







812,000 



1,040,000 



82,000 



101,000 







690,000 



0-6 



620,000 



41,000 



40,000 







230,000 



t Also Azotobacter, 1 colon3' = 41,000 per gram. 

 * The reaction of the medium as prepared was sucii that 10 c.c. had an 

 acidity = + 1 of Fuller's scale, i.e., 100 c.c contained the equivalent of Ice. 

 of N/1 acid. The capillary pipette, which was used for neutralising or 

 augmenting the acidity, was of such calibre that 50 drops=lc.c. The 

 addition of 1 drop of N/1 carbonate of soda to 10 c.c. of medium changed 

 the reaction from +1 to +0'S. 



EXPERIMKNT iii. 



