ABSTRACTS 95 



Are Spore-Forming Bacteria of any Significance in Soil Under Normal 



Conditions? H. Joel Conn. 



A series of tests has been made at the New York Experiment Station 

 to determine whether B. mycoides, B. cereus and B. megatherium, 

 the most common spore-forming bacteria in soil, occur under normal 

 conditions as spores or as vegetative rods. Diluted soil infusion was 

 heated at a temperature of 75 to 85°C., heated and unheated samples 

 of the infusion plated, and the colonies of these three types on the two 

 sets of plates counted. It was assumed that the colonies on the plates 

 from heated infusion represented spores and that the difference in 

 favor of the unheated infusion, if any, represented the vegetative forms. 



In a series of 22 tests the average count of all three spore-formers 

 was: 775,000 per gram, unheated; 726,000 per gram, heated. They 

 were higher 14 times in unheated infusions, 8 times in heated. The 

 greatest difference in favor of the unheated infusion was 530,000 per 

 gram, which was offset by a difference of 450,000 in favor of the heated 

 infusion; a fact which suggests that both were within the limits of 

 experimental error. Considering the organisms separately: 



B. mycoides was higher 12 times in unheated infusions, 8 times in 

 heated. 



B. cereus was higher 10 times in unheated infusions, 8 times in 

 heated. 



B. megatherium was higher 12 times in unheated infusions, 8 times 

 in heated. 



The number of spores or the total number of spore-formers present 

 did not increase even in a pot of soil mixed with a heavy application of 

 fresh horse manure. 



These figures suggest that bacteria of this group normally occur in 

 soil only as spores, in which form they cannot be active. This is 

 surprising, as they are universally present, and have always been 

 considered important. What their actual significance may be is a 

 question. 



Ferrification in Soils. P. E. Brown and G. E. Corson. 



Preliminary studies of the oxidation of iron in the soil, or ferrifi- 

 cation, have shown that the process is rather a complicated one. An 

 attempt was made to ascertain whether soils have a ferrifying power, 

 whether such a power is bacterial or chemical in nature or the result 

 of a combined action of several groups of factors, whether different 

 soils have varying ferrifying powers, whether ferrification can be 

 measured in the laboratory and finally whether the process is of any 

 significance from the soil fertility standpoint. 



Much difficulty was experienced in devising methods for the work, 

 owing to unsatisfactory chemical methods and many series of tests 

 were carried out merely to solve some of the chemical problems in- 

 volved. A method has been devised which, although still rather crude, 

 will permit of tentative conclusions. 



Soils from a wide variety of sources were tested and it appears that 

 ferrification is a process of common occurrence in the soil, that different 



