Length of Time to Incubate Petri Plates. 107 
TABLE IV. 
Percent 5 and 7-Day Counts are of 10-Day Counts. 
(Air Dry Loam sieved to pass 60 mesh.) 
Time oF INCUBATION 5 (f 10 Days* 
Sample No. Size of Sample 
leona becoub oe 50 grams 79.9% 96.8% 100.0% 
Dr a2 ARE RE 50 grams _67.0 100.0 100.0 
OE ed eee eee 50 grams 89.8 100.0 | 100.0 
ae 10 grams @307 72.1 | 100.0 
Hho dia bos de eoeeeaee 10 grams 72.6 91.0 100.0 
(hes DACRE eee 10 grams 74.7 100.0 100.0 
WEEE cae aise «5% 5 grams 85.2 93.2 100.0 
Ge hide oC eee 5 grams 90.8 95.7 100.0 
Le oho ee ee Sees 5 grams 63.4 73.2 100.0 
Ee sik s wiact a: 1.0 gram 93.7 100.0 100.0 
Te a ass ee eee 1.0 gram 63.6 75.3 100.0 
Lk Snel oeicieda ae eae aes 1.0 gram 62.8 85.8 100.0 
GS 3546 Qoeeo eee eee 0.5 gram 64.3 ont 100.0 
ii eb ROSE eae See 0.5 gram 66.5 100.0 100.0 
INS go) Repent 0.5 gram 74.9 Uithets 100.0 
AVCTAGC, cm crn seine 2 | 74.2 88.9 100.0 
*Counts after 10 days incubation at 20°C taken as 100%. 
Other counts stated as parts of these Bacterial dilution 1-400,000. 
The results given in the previous tables show: 
1. That the greater proportion of the organisms present in this 
air-dry soil develop into colonies after five days’ incubation. 
2. The larger the aliquot of soil used the more uniformity be- 
tween the development of colonies on the plates. 
In five cases out of the fifteen all the colonies were counted 
co 
after seven days’ incubation when the soil was sieved to pass 
a sixty-mesh sieve. 
It has been observed, in soil bacteriology investigations in an apple 
crchard where different systems of soil management are practiced, that 
the organisms multiply into colonies at different rates, dependent on the 
system of management practiced. 
in Table V. 
The results of this work are given 
