316 BOTANICAL GAZETTE [OCTOBER 
in their nitrifying power, would be a matter of considerable inter- 
est. Since it is likely that the humus content of a soil most 
intimately of all factors controls its nitrifying efficiency, it was 
decided to observe the effect of the addition of sugar to these soils 
in comparison with that produced by the addition of lime. Accord- 
ingly, two 100 gm. portions of each soil were measured out into glass 
jars, the moisture content brought up to 20 per cent, and the jar 
placed in the incubator room. To one portion of the soil 0. 15 per 
cent CaCo, was added, and to the other 2 per cent of mannite. 
After 3 weeks, a period allowed for the lime and sugar to exert some 
influence on the bacterial flora, an optimum moisture content being 
maintained, o. 1 per cent ammonium sulphate was added to measure 
the nitrifying power of the soils. All of these soils, it will be 
recalled, had been tested for nitrifying power without the addition 
of lime, and a threefold comparison was thus afforded. Table III 
gives the quantities of nitrates found with and without lime. 
TABLE III 
COMPARATIVE NITRIFYING POWER OF CERTAIN SOILS WITH AND WITHOUT LIME 
MG. OF NITRATE NITROGEN MG. OF NITRATE NITROGEN PER 
PER I00 GM. SOIL I00 GM. SOIL 
No. No. ' 
Without Caco,| With o.15 per Without Caco, | Wi (285, 
ee eer eer ee ee ay Terr cus arr i ae a Ae ees aa dee 2,12 
Be ele ers r.§ PP OE PE 0.6 7.6 
Bo a eee a ee Pe 1.8 7-3 
Be PS eae ee ER eee peor eer | beets EUnet" 1.4 
Oe re ee 4.3 8.8 far t.4 8.8 
Ooo celoe ss BUX 5 pt eee cranes anaes ae re ng 
OT ee ES cP © aMleercy PUPS crane yeast as EG keen lcs I I 
Breve. 72 12 ps Pare 3 5 
| at eee ad ire War eer ery mere re ye BE aos iS: I T 
io Raa eas 6.5 1.6 7 de asen tl scents 4 W eae rar per car Gur a Trace 
EY oii Oe ee a oe re oF eae ge I t 
je A roe ae Pe I 
~ Without the use of lime a number of soils completely failed to 
nitrify ammonium sulphate, and few exhibited what might be 
termed an average nitrifying power as judged by the method 
employed. While under the influence of lime there is an increase 
in the majority of the soils, although the stimulation is not especially 
