21G 



ManHriiKj for Ihuf 



the aiuouiit of amiiioiiia produced is greatly indueiiced by the supply 

 of peptone, but that in all cases the rate of production falls greatly 

 after about 50 GO hours' incubation. This latter conclusion was in the 

 main borne out by similar tests with other soils, but deviations from 

 the general rule were not lacking. 



On repeating now the comparative tests with the different soils, 

 using 100 c.c. of the 1 per cent, peptone solution and estimating the 

 amnioiiia present after different periods of incubation, much more 

 marked differences were found than those recorded in Table XI. The 

 following comparison of the best and worst plots will serve as an illustra- 

 tion (see also Fig. 3). For convenience of comparison the amount 



30 40 50 60 70 80 90 100 

 Hours of Incubation 

 Fig. 3. 



of niiniioiiia produced by I'lot 12 after 18 hours' incubation is taken 

 as 100. The figures in brackets give the amounts for Plot 2, taking 

 the amount for Plot 12 for the same period as 100. 



Relative Amounts of Ammonia produced during 



24 hrs. 48 lirs. 57 hns. 72 his. 79 hrs. 96 lirs. 103 hrs. 

 Plot 2 29 1U4 171(130) 175(117) 179(114) 180(111) 180(101) 



Plot 12 NU 100 132 150 157 1G2 179 



