BACTERIA OF OLD SOILS 



105 



bacterial activity and the character of the soil, that a brief tabu- 

 lated description of the soils be presented : 



The soils 



NO. 



LAB. NO. 



DESCRIPTION AND ORIGINAL LOCALITY 



1 



15 



Alkali soil — Westminster, Orange County, California 



2 



30 



Alkali soil — Westminster, Orange County, California 



3 



5 



Adobe ridge — Surface soil. Campus, University of California 



4 



4 



Adobe ridge — Sub-soil, Campus, University of California 



5 



1 



Adobe — 10 to 20 inches in depth Campus, University of Cali- 







fornia 



6 



8 



Loam — Stockton, California 



7 



6 



Black adobe — 6 to 12 inches in depth, Stockton, California 



8 



51 



Foothill sandy red soil — 1 to 12 inches in depth. Auburn, 







California 



9 





Rich loam — Huerohuero, San Luis Obispo County, California 



These soils represent a variety of types, from the heavy adobe 

 to the Hghter red sandy soils, from the deeper sub-soils to the 

 surface soils, from the Stockton soils, rich in organic matter, to 

 the poorer foothill sands, and from the alkali soils typical of 

 the arid west to the normal soil free from excessive amounts of 

 injurious salts; This diversity in the soils which were used 

 permits of a wider application of the facts obtained. 



THE NUIVIBER OF ORGANISMS 



Although it has been observed that the physiological efficiency 

 or organisms in bringing about chemical transformations bears 

 little or no relation to the number present, it appeared of interest 

 to determine the number of bacteria still retained in the dried 

 soil, in order to observe any correlation between numbers and 

 physiological power that might obtain, but more particularly for 

 the sake of learning the effect of the drying on the numbers in 

 the various soils, comparing the count found with that of freshly 

 sampled soils. 



The count was made by placing 1 gram of soil weighed in a 

 sterile platinum dish into 100 cc. of sterile water and shaking 

 for three minutes. From this suspension other necessary dilu- 

 tions were prepared with sterile water blanks and sterile pipettes. 



