AGEICTJLTUEAL BOTANY, 327 



ously and that there does not have to be a complete or even lai'ge depletion of 

 soil nitrogen before the nodule-forming processes begin. 



Some bacteriological relations in soils kept under greenhouse conditions, 

 J. G. LiPMAN and I. L. Owen (Jonr. Agr. 8ci., 3 (1910), No. 3, i)p. SOl-310).— 

 The results are given of the effects of varying quantities of acid phosphate 

 and citric acid on the number of colonies on agar plates, the influence of small 

 additions of fertile soil on the bacterial content of quartz sand properly sup- 

 plied with plant food, the number of bacteria in greenhouse soils as affected 

 by the addition of organic matter and of cultures of Bacillus mycoidcs, and 

 the influence of gypsum on the number of soil bacteria that form colonies on 

 ngar plates. 



Considered in their entirety, these experiments indicate that in greenhouse 

 soils there may be at first a very rapid increase of decay bacteria to numbers 

 above the normal and then a gradual decline to numbers decidedly below the 

 normal, while the nitrifying organisms become more prominent as the others 

 gradually decrease. There were indications of periodicity in the increase and 

 decrease of the decay bacteria in the soil, and it is possible that with a much 

 loiiger period of observation, the numbers of bacteria-producing colonies on 

 agar plates would rise again to very considerable proportions. 



On measuring' the activity of aerobic bacteria in the soil by the amount 

 of carbon dioxid produced, F. H. Hesselink van Sltchtelen (Ccntbl. Bakt. 

 [cfc], 2. Ahf., 28 (1910), No. 1-3, pi). J,5-89, fig. J).— The author gives the re- 

 sults of experiments on the activity of soil micro-organisms, in which the 

 amount of carbon dioxid evolved is used as a means of determining the in- 

 tensity of their activity. By this method the effects on bacterial activity of 

 pulverization, aeration, water content, frosts, the addition of different substances 

 to the soil, such as dextrose, mannit, straw, minerals, .etc., and of the partial 

 sterilization of soils by carbon bisulphid, were tested, as well as the activity 

 of soil bacteria at different depths and in different soils. 



The method consists of passing a measured quantity of carbon-dioxid-free 

 air for a given time through S-liter flasks, each containing usually 6 kg. of the 

 soil at a temperature of from 10 to 12° C., and then measuring the quantity 

 of the carbon dioxid evolved. 



Comparisons made of the results obtained by this method and those obtained 

 under similar conditions by plate cultures show in many instances approxi- 

 mately equivalent results for the activities tested. It is therefore claimed 

 that by the carbon dioxid method one can determine with accuracy the more 

 important factors which influence the bacterial life of the soil, especially under 

 ordinary field conditions. 



The assimilation of ammonia, nitrate, and amid nitrogen by micro- 

 organisms, S. BiEREMA (Die Assimilation von Ammon-, Nltrut-, und Amiil- 

 sticlxstoff (lurch Mikroorganlsmen. Inaug. Diss., Leipsic, 1909, pp. 83, pis. 7; 

 ahs. in Jahreshcr. Lamln:, 2.'f (1909), p. Jfl). — The author claims that the 

 microbiological utilization of most nitrogen compounds occurs both in crudt» 

 and pure cultures under suitable conditions, that is, when the appropriate 

 carbohydrate is present as a source of energy. He also states that molds can 

 assimilate nitrogen compounds. 



A further contribution on white mustard in its relation to nitrogen assimi- 

 lation, O. Lemmermann et al. (Landw. Vers. Stat., 73 (1910), No. 6, pp. Jf2.5- 

 1,56; abs. in Illus. Landw. Ztg., 30 (1910), No. 75, p. 709).— In a series of experi- 

 ments similar to those previously reported (E. S. R., 20, p. 717), it was found 

 that during the growing period soils on which white mustard was grown had a 

 slight, but plainly evident, nitrogen increase over similar plant-free soils, but 



