24 EXPERIMENT STATION RECORD. 



ferent races of these organisms showing great variations in virulence were 

 distinguished in the different soils. It is stated that the races found in com- 

 post beech forest soil, and peat may be combined into one great group in con- 

 trast to the race found in cultivated soil, and that the respective powers of 

 transformation of these two groups stand in the ratio of 4 : 1. 



Nitrate destruction increased in both soil and nutritive solution with an 

 increasing thiosulphate content or increasing nitrate content. Nitrate could 

 not be replaced as a source of oxygen by other compounds containing oxygen. 

 It was possible to replace thiosulphate as a source of energy for the bacteria 

 in question by other sulphur compounds but not by compounds not containing 

 sulphur Carbonate and bicarbonate were equally effective as sources of carbon. 

 The addition of thiosulphate to soils caused a strong denitrification, which 

 was not, however, as strong as that caused by the addition of organic matter. 

 The thiosulphate bacteria, by nitrate destruction, showed the same effect upon 

 the physical condition of the soil as is attributed to the heterotrophic denitri- 

 fying bacteria by Koch and Pettit (E. S. R., 23, p. 123). 



It is thought that the results obtained in these studies will serve to explain 

 the results of a previous work of Thalau on the effect of sulphur compounds 

 on plant growth (E. S. R., 29, p. 521). 



The formation of leaf mold, F. V. Coville (Ann. Rpt. Smithsn. Inst, 1913, 

 pp. 333-3Ji3).— This is a revisi(^ of an article which has already been noted 

 from another source (E. S. R., 28, p. 814). 



Soil tank experiments, S. E. Collison (Florida Sta. Rpt. 19U, pp. LXXVII- 

 LA'i'/X).— Experiments with fertilizers for citrus trees were continued as in 

 previous years (E. S. R., 31, p. 723), the data for composition of the drainage 

 water obtained being tabulated. 



It is stated that the losses of potash have continued to increase, being con- 

 siderably larger than for the same period of the previous year. The opposite 

 is noted with reference to nitrogen and the lime losses continue large. "The 

 presence of comparatively large amounts of ammonia as such, in the water 

 from tanks 1 and 2, indicates that a portion of the sulphate of ammonia applied 

 loafhed through without being nitrified." 



The orig'in, composition, aud fertilizer value of the bat guanos of Cuba 

 and the Isle of Pines, C. N. Ageton {Modern Cuba, 3 {1015), No. 2, pp. ^8- 

 59). — On the basis of analyses of samples from Cuba, Porto Rico, and Haiti it 

 is stated that average bat guano contains from 3.5 to 7 per cent of phosphoric 

 acid, 1.5 to 3 per cent of potash, and 8 to 11 per cent of nitrogen but varies 

 widely in composition, depending upon the stage of decomposition, moisture 

 content, leaching, admixture of foreign substances, and other conditions. " The 

 fresh, friable bat excrement, which usually occurs as a thin covering over the 

 floor of the cave, may easily be distinguished from the other classes of material. 

 A light colored deposit may be expected to contain considerable quantities of 

 ralcium carbonate or gypsum, or both, the phosphoric acid content being quite 

 variable but usually higher than in the fresh guano. The reddish or chocolate 

 colored deposits or parts of deposits which have much the same appearance as 

 a red or ' mulatto ' soil, contain more phosphoric acid than the others, and 

 usually they contain but very little, if any, nitrogen." 

 The use of the guano as a fertilizer is discussed. 



The utilization of the nitrogen and organic matter in septic and ImhofE 

 tank sludges, C. B. Lipman and P. S. Burgess {California Sta. Bui. 251 {1915), 

 pp. 287-2.9.5).— ^Analyses of a number of samples of the sludges are reported 

 Hhowing nitrogen varying from 1.23 to 2.66 per cent and phosphoric acid from 

 0.77 to 1.82 per cent. An attempt was made to judge of the availability of the 

 nitrogen of the sludges by determining its rate of nitrification when mixed 



