SOILS — FERTILIZERS. 817 



The importance of colloid substances in the soil from an agricultural 

 standpoint, P. Kohland {Monatsh. Landio., 6 (1913), No. 9, pp. 263-265).— The 

 relation of colloids to the physical and chemical properties and processes and 

 biological activities in the soil is briefly discussed. 



Bacterial activity in soil as a function of the various physical soil prop- 

 erties, O. Rahn (Science, n. ser., 38 {1913), No. 977, pp. 414, 415).— This ques- 

 tion was studied with pure cultures of Bacillus mycoides grown in quartz- 

 sand peptone water mixtures, the amount of ammonia formed being taken 

 as an indicator of the bacterial activity. Studies were also made with Bac- 

 terium JactiH acidi grown in milk-sand mixtures, acidity and number of cells 

 serving as a measure of development. 



It is shown that conclusions from the results are greatly influenced by the 

 basis of comparison used. The author concludes that the efliciency of bacteria 

 can be determined only by comparing equal amounts of culture medium and of 

 food. The bacterial activity is influenced greatly by the extent to which the 

 medium is favorable or unfavorable to oxygen exchange, also by the thickness 

 of the moisture film surrounding the soil particles, that is the thinner the 

 film of moisture (within limits) the more rapid the changes. It is estimated 

 that in arable soils with particles not more than 0.1 mm. in diameter, it would 

 require more than 50 per cent of moisture to produce the optimum film thick- 

 ness, so that it is probable that strictly aerobic bacteria will never find optimum 

 conditions in soils. On imitating the effects of undecomposed organic matter 

 by adding finely ground filter paper to sand, it was found that in fairly dry 

 soils such addition of cellulose caused a decrease of ammonia formation by 

 making some of the soil moisture unavailable for bacteria. In the moister 

 sands the addition of cellulose increased ammonification, probably by holding 

 the sand particles further apart, and thus increasing aeration. 



The orig'in of certain organic soil constituents, M. X. Sullivan (Science, 

 n. set:, 38 (1913), No. 977, p. 4H)- — This is an abstract of a paper presented 

 before the Society of American Bacteriologists. 



It is reported that the following substances were found as products of the 

 growth of Penicillium glaitcum in Raulin's solution : Hypoxanthiu, guanin, 

 adenin, histidin, thymin, cholin, probably lysin, oleic and palmitic acids, a 

 fatty acid melting at 54° C, hydroxy-fatty acids, cholesterol bodies, cerebrosid, 

 mannite. pentose sugar, and unidentified aldehydes. Since most of these com- 

 pounds have been found in soil, the conclusion is drawn " that in the forma- 

 tion of the various organic soil constituents, micro-organisms, such as yeasts, 

 bacteria, and molds, play an important part." 



Characteristics of cellulose-destroying bacteria, I. G. McBeth, F. M. Scales, 

 and N. R. Smith (Science, n. ser., 38 (1913), No. 977, p. 41.5).— This is an ab- 

 stract of a paper presented before the Society of American bacteriologists. 



" The cellulose-destroying organisms are divided into the following groups : 

 (1) Those which give an acid reaction from all of seven peptone carbohydrate 

 solutions used, (2) those which give an alkaline reaction from all of the pep- 

 tone carbohydrate solutions, (3) those which give an acid reaction from only 

 a part of the peptone carbohydrate solutions, and (4) those which produce no 

 change in the reaction of any of the peptone carbohydrate solutions." 



Experiments on denitrifi.cation, F. V. Chirikov and A. A. Shmuk (Izv. 

 Moskov. Selsk. Khos. Inst. (Ann. Inst. Agron Moscou), 19 (1913), No. 2, pp. 

 270-286, pi. 1, figs. 3; abs. in Internat. Inst. Agr. [Rome], Mo. Bui. Agr. Intel, 

 and Plant Diseases, 4 (1913), No. 10, pp. 1528, 1529). — The influence of moisture 

 and increasing amounts of straw on the progress of denitrification in sandy 

 loam soil was studied in these experiments. 



