556 ABSTRACTS 



mined for these three molds after 6, 12 and 18 days upon a culture 

 medium composed of gravelly loam plus dried blood and cotton-seed 

 meal as ammoniates. From results of this preliminary experiment at- 

 tempt was made to determine how the biological stage affected ammoni- 

 fication. The periods of most active ammonification correspond to those 

 of active spore formation for the respective organisms and the small- 

 est amount to the time preparatory to actual spore formation. The 

 Monilia shows the largest ammonia accumulation within the first 3 or 

 4 days; the Penicillium, between 10 and 15 days and the Mucor be- 

 tween 6 and 10 days. 



An analogy is found in the growth of legumes like the clovers. Nitro- 

 gen is fixed during the period of active growth of the plant, the fixation 

 ceasing almost entirely when seed formation begins. — Z. N. 



Diastase Activity and Invertase Activity of Bacteria. George P. 



Koch. (Soil Science, 1916, 1, 179-196.) 



This paper is limited to the study of diastases and invertases pro- 

 duced by bacteria which are concerned in the production of nitrogen 

 compounds for consumption by plants and in the decomposition of 

 carbohydrates in the soil. 



The author determined that sufficient diastases and invertases were 

 secreted by bacteria so that they could be quantitatively determined 

 and also that there was considerable variation in the enzyme (diastase 

 and invertase) secretion by organisms developed in culture solutions of 

 different composition. The enzyme secretion by bacteria at different 

 periods varies from day to day under conditions otherwise the same 

 and there seems to be no direct correlation between hydrolytic enzyme 

 secretion by bacteria and their property of decomposing proteins. 

 The enzyme activity of various organisms and their ability to decom- 

 pose proteins vary greatly; there is also a variation in enzyme activity 

 of different cultures of the same species. No correlation was found be- 

 tween the secretion of enzyme and the decomposition of proteins by 

 bacteria, the property of the cultural solution to rotate the plane of 

 polarized light, the percentages of reducing compounds, the formation 

 of acid or the numbers of organisms. 



The rotatory power of a solution may be increased as well as de- 

 creased by bacteria; they do not produce a surplus of reducing com- 

 pounds. Bacteria also seem to have the property of causing a condi- 

 tion which will prevent starch hydrolysis and sucrose inversion. There 

 may be a possible correlation between the protein decomposition de- 

 termined as ammonia and the formation of acid. — Z. N. 



Bacterial Numbers in Soils at Different Depths, and in Different Seasons 

 of the Year, Selman A. Waksman. (Soil Science, 1916, 1, 363-380.) 

 Four soils were studied. Meadow soil gave the largest bacterial 

 counts at a depth of 1 inch, the 1-inch layer of this soil being richer 

 also in organic matter and nitrogen content than that of the garden 

 and orchard soils. The forest soil, though showing a high carbon and 



