814 EXPEBIMENT STATION RECORD. [Vol.36 



of methods of determining iron in soil and of the ferrifying power of soils are 

 reported. The conclusions reached are as follows : 



" Ferrification and deferriflcation are processes common to the soils used in 

 this study. The degree of ferrification and deferriflcation may depend upon 

 many factors, such as organic matter content of the soil, cultivation, moisture, 

 temperature, and food supply. An incubation period of one week in solutions 

 is not sufficient time to allow the organisms to develop and bring about ferrifi- 

 cation. There is no relation between the organic matter content of the soil 

 and its ferrifying power when solutions are used. The cultivated soil has the 

 greatest ferrifying power. Sterile water to which is added 0.1 gm. of ferrous 

 carbonate is the best medium for the growth of the biicteria causing ferrifica- 

 tion in solutions. 



" Sand, with the addition of 0.1 gm. of ferrous carbonate and maintained at an 

 optimum moisture content with distilled water, represents more nearly the condi- 

 tions of moisture, temperature, and aeration in the field than do the solutions. 

 When sand is used as a medium for the gro^vth of the bacteria, it appears that 

 the ferrifying power of the soil is related to its organic matter content. Where 

 there was a high percentage of organic matter, there was a corresponding 

 increase in ferrification. When the soil was low in organic matter, deferrifica- 

 tion took place. 



" The use of pure cultures of bacteria indicates that the common soil organ- 

 isms, as well as the iron bacteria, are able to bring about ferrification. Molds 

 as well as bacteria are capable of oxidizing ferrous iron." 



A list of 16 references to the literature of the subject is given. 



Contributions to our knowledge of soil fertility. — XII-XIV, R. Greig- 

 Smith {Proc. Linn. Soc. N. S. Wales, 39 (1914), pt. 4, Nos. 156, pp. 839-850; 

 160, pp. 631-645, 724-733).— Three studies are reported. 



In the first paper the action of toluene on protozoa in different soils is taken 

 up. With a poor alluvial soil in moist condition it was found that the ciliates 

 survived a treatment of 1.5 per cent toluene and were killed by 2 per cent, 

 while amcBbse survived a 2 per cent treatment. In the air-dried soil the ciliates 

 and amcebse survived a 20 per cent treatment. With a sandy soil in moist con- 

 dition ciliates survived 1 per cent and were killed by 2 per cent toluene, and 

 amoebse survived 2 per cent but were killed by 5 per cent. In the air-dried soil 

 both ciliates and amoebae again survived 20 per cent toluene. 



The theory that certain bacteria may have an influence upon the develop- 

 ment of the fauna in treated soils was not substantiated. It was further found 

 that " if the conditions are such that a reduction of sulphate is possible, as, 

 for example, in soils containing much organic matter, there is the possibility 

 that the action of a volatile disinfectant, by destroying some of the groups of 

 the sulphur-oxidizing bacteria, may indirectly affect the growth of the protozoa, 

 and especially of the ciliates." 



In further tests of air-dry soils, " treatment with varying quantities of 

 toluene showed that all percentages up to 20 failed to destroy the protozoa, 

 taking Colpoda cucullus as being typical of the ciliates, Cercomonas or Tre- 

 pomonas as representing the flagellates, and the usual Amccba Umax or lobosa 

 for the amoebae. . . . The experiments show that there is considerable irregu- 

 larity either in the effect of the disinfectant or in the capability of growth 

 after treatment. It appears that toluene has little disinfecting action when 

 the moisture content is lower than from one-tenth to one-twentieth of the water- 

 holding capacity of the soil and that when soils are quite moist amoebae and 

 flagellates may not be affected to any great extent. ... It appears to make no 

 difference whether the water is originally present in the soil or is added at the 

 time of toluening. , . . Omitting the flagellates, which appear irregular, the 



