318 



SCIENCE 



[N. S. Vol. XLII. No. 1079 



teria. This seems rather to be a result of increase 

 in the number of cells than increase in individnal 

 cell activity. 



All of the phosphates gave a large increase in 

 the number of soil bacteria. There was only a 

 slight increase from the sulphates. 



The same relative effect of phosphates and sul- 

 phates was noted in the case of carbon-dioxide 

 evolution. 



From the results of this work, as a whole, the 

 foUowing conclusion may be drawn: 



That possibly the increased crop production 

 which results from the application of soluble phos- 

 phates is due in part to the promotion of bacterial 

 activity. 



The details will appear in a future publication. 

 The Effect of Green Manures on the Germination 



of Various Seed: E. B. Feed. 



When green manures are turned under and the 

 SOU planted immediately, a decrease in germina- 

 tion may result.^ 



This problem was considered of sufficient im- 

 portance to warrant a series of field and labora- 

 tory experiments in an endeavor to find some ex- 

 planation for this phenomenon. The causes that 

 might be offered to account for the harmful influ- 

 ence of green manures on seed germination are : 



First, that the green manure not only causes a 

 marked increase in number of bacteria, but also a 

 change in the flora. 



Second, that the great increase in number of 

 bacteria results in a possible accumulation of some 

 substance or substances, toxic to germination. 



Third, that the rapid multiplication of microor- 

 ganisms greatly increases their metabolism. 



In order to gain some idea of the practical im- 

 portance of this problem, a series of field tests was 

 conducted. The results of this work show that 

 when green clover or oat tissue is turned under 

 and the land planted immediately, there is a dis- 

 tinct decrease in the rate of germination with cot- 

 ton, soy bean and hemp seed. The cereals, corn 

 and oats fail to show any injury from green ma- 

 nures. After twenty -five days the injurious factor 

 seems to have disappeared entirely. 



Under greenhouse conditions it has been found 

 that small 'amounts — 0.25 per cent. — of green ma- 

 nures are injurious to the germination of cotton 

 seed. Larger amounts are more effective. 



The addition of calcium carbonate to the green 

 manure fails to prevent the injurious action. 



The degree of retardation seems to vary some- 

 what with the soil type; in heavy soils green ma- 



6 Hoffman, Exp. Sta. Bull. 228, 1913, p. 26. 



nures have their most marked effect; furthermore 

 an increase in moisture causes a decrease in rate of 

 germination. 



When peptone and casein are added in the 

 same nitrogen ratio as the green manure, no de- 

 crease in germination is noted. Soluble carbo- 

 hydrates in amounts of 1 to 2 per cent, retarded 

 the rate of germination, but did not cause the seed 

 to decay as in the case of green manures. 



Determinations of carbon dioxide and ammonia 

 in green manure soils were made. Periodic anal- 

 yses failed to show the presence of these in quan- 

 tities great enough to account for the injury to 

 seed germination. 



A more complete report of this work will appear 

 in bulletin form. 



Standard Methods of Bacteriological Analysis of 



Milk: H. W. Conn. 



Professor Conn gave an account of an extended 

 series of cooperative experiments in four labora- 

 tories in New York upon the reliability of the 

 bacteriological examination of milk, and as a re- 

 sult of the facts that were brought out by the co- 

 operative tests, reported that the Committee on 

 Standard Methods of the American Public Health 

 Association had made the following changes in 

 methods of milk analysis. 



First, that beef extract (Liebig) be substituted 

 for beef infusion in the making of agar media. 



Second, that 1.2 per cent, dry agar or 1.5 per 

 cent, ordinary moist agar be the amount used in 

 standard medium. 



Third, the acidity of standard medium shall be 

 1 per cent. 



Fourth, all plates shall be incubated at 37* de- 

 grees for 48 hours before counting. 



Fifth, plates shall be counted with a magnifying 

 power of 3 J diameters. 



The AlTcali- forming Bacteria Foimd in MiVc: S. 



Henry Ayers and Philip Eupp. 



The alkali-forming bacteria may be broadly de- 

 fined as those which produce an alkaline reaction 

 in milk within 7 days, due to the oxidation of salts 

 of organic acids, which results in the formation of 

 alkali carbonates. No visible sign of peptoniza- 

 tion is produced. 



Probably all the alkali-forming bacteria produce 

 ammonia upon long inoculation, but the prelimi- 

 nary alkaline reaction is due to the production of 

 alkali carbonates and not to ammonia. The pres- 

 ence of alkali carbonates in milk can be deter- 

 mined by the addition of casein dissolved in 

 sodium phosphate. 



