824 EXPERIMENT STATION KECOED. 



AGRICTJLTUEAL BOTANY. 



Methods for bacteriological examination of soils, P. B. Brown (Iowa 8ta. 

 Research Bui. 11, pp. 381-407; CcntU. Balct. [etc.], 2. Aht, 39 (1913). No. 1-S, 

 pp. 61-73). — In this paper the author reviews the methods that have been sug- 

 gested for the bacteriological examination of soils, and gives the results of 

 studies on different media for the quantitative determination of bacteria in soils. 



In the bacteriological examination of soils various objectionable features have 

 been found in the different methods, and the author reports studies to deter- 

 mine their relative efBcieucy. According to the author, fresh soil is the most 

 rational medium for studying the physiological activities of soil bacteria. An 

 albumin solution may serve as a measure of ammonifieation and is preferable to 

 dried blood, but it possesses the disadvantage that it is very difficult to prepare. 

 A solution of casein proved quite satisfactoi-y as a measure of ammonifieation 

 and did not possess any of the disadvantages of the other nitrogenous materials. 

 Slight variations in moisture conditions in field soils did not appear to affect 

 materially the ammonifieation of casein. Ten cc. of a 10 per cent solution of 

 casein was found to be the best amount to use for 100 gm. of fresh soil, and the 

 optimum incubation period at room temperature was found to be 3 days. 



In studying the media for the quantitative determination of bacteria in soils 

 the author found that albumin agar permitted the development of much larger 

 numbers of bacteria than the modified synthetic agar or any other medium 

 tested, except an artificial humus agar. Casein agar permitted the development 

 of bacteria, but in smaller numbers than the albumin agar. An artificial humus 

 agar yielded practically the same counts as were obtained with albumin agar. 

 The difficulties in the preparation of this material and the fact that it is not in 

 any way superior to albumin agar led to the recommendation that the latter 

 medium be employed. Media prepared from soil extracts permitted fewer 

 organisms to develop than the modified synthetic agar. 



A new method for the bacteriological examination of soils, P. E. Brown 

 (Science, n. ser., S8 (1913), No. 977, p. 413). — This is an abstract of a paper 

 presented before the Society of American Bacteriologists. 



" The method recommended consists in testing of fresh soil obtained as de- 

 scribed in previous work by the author [E. S. R., 26, p. 428], adding a solution 

 of casein for ammonifieation, ammonium sulphate for nitrification, and mannite 

 for nitrogen fixation." 



Nitrogen collecting bacteria, fallow, and exhaustive culture, T. Pfeiffeb 

 {Stickstoffsamviclnde Bakterien, Brache und Raubbau. Berlin, 1912, 2. ed., rev. 

 and enl.. pp. 100). — This is a second enlarged and amended edition of the work 

 previously noted (E. S. R., 16, p. 858). 



Can fungi living in agricultural soil assimilate free nitrogen? H. N. 

 GoDDARD (Bot. Gas., 56 (1913), No. /,. pp. 249-305, figs. iS).— The investigation 

 described in this paper was begun to determine what species of fungi live 

 habitually in ordinary agricultural soil, to study their distribution as to the 

 depth and nature of the soil, and to ascertain the part they play in soil fer- 

 tility. About 17 species were isolated and studied when attention was turned 

 to the subject of nitrogen-fixing power. 



Summarizing his results, the author states that many species of fungi live 

 habitually in the soil, some of them not thus far having been found elsewhere. 

 These appear rather uniformly distributed at different depths, at least as low 

 as 14 cm. Tillage and manuring, so far as observed, seem to produce little 

 chsnige in the number or kind of fungi present. It was found that the fungi 

 could be readily cultivated and isolated, and of the forms studied, including at 



