Physiologie. . 389 



or nitritication. This confirms the observations of previous workers. 



Large amounts of elemental sulphur cause a decrease in tlie 

 total nuraber of bacteria that grow on agar plates, but produce an 

 increase in ammonification at concentrations of 0.05 per cent, This 

 increase in ammonia is accompanied by a parallel decrease in ni- 

 trate formation. The decrease is very probably due to the acidity 

 or toxicity produced by the oxidation of sulphur. 



Calcium sulphate stimulates the growth of pure cultures of red- 

 clover bacteria in nutrient Solutions and in soil extract. The increase 

 is as great with O.Ol per cent as with 0,1 per cent. 



The root development of red clover is increased by calcium 

 sulphate, O.Ol per cent being apparentl}»- as efficient in producing 

 this increase as 0.1 per cent. 



In small amounts calcium sulphate increases the yield of red 

 clover and also the number of nodules. Concentration as high as 

 0.5 to l per cent, however, produces no increase in growth. 



The application of elemental sulphur to silt-loam soil increased 

 but slightly the jneld of clover and apparently did not affect root 

 development or nodule formation. In producing this slightly increa- 

 sed growth 0,01 per cent was as efficient as were higher concen- 

 trations. 



A review of the results of these experiments shows that calcium 

 sulphate in soil does not produce any marked effect on the bacteria 

 commonly found on agar plates, but does increase the growth of 

 the legume bacteria. It also increases the yield of red clover, which 

 is accompanied by a greater root development and a greater num- 

 ber of nodules. 



The addition of sulphur increases the ammonification, but de- 

 creases nitrification and the total number of soil organisnis. It in- 

 creases the yield of red clover but slightly and does not affect the 

 root development nor the number of nodules. 



M. J. Sirks (Wageningen). 



Willaman, J. J. and R. M. Ws-^t. E ff ect of clim atic factors 

 on the hydrocyanic-acid content oi Sorghum. (Journ. agr. 

 Research. Washington. VI. p. 261—272. 1916.) 



Two varieties of sorghxxra {Andropogon sorghuin) , Southern Cane 

 and Early Araber, were grown by the writers on plots in Minne- 

 sota, Utah, Kansas and South Dakota under widel3'- different 

 climatic and cultural conditions. The amount of the glucosid dhur- 

 rin in each plot varied considerably. The following correlations 

 relative to the amount of glucosid were found to exist: 



Unhealthy plants usually contain more hydrocyanic acid than 

 healthy ones. The unhealthj'- condition may be due to malnutrition, 

 to improper transpiration, to insect attack, or to other causes. It is 

 possible that under such conditions the plant produces more gluco- 

 sid for the sake of the stimulating hormones in it. 



The apparent effect of humidity and temperature on the amount 

 of Cyanid in sorghum is probably due to the indirect effect on the 

 rate of growth. 



Adequate water supplj?- is usually accompanied b}' low, and 

 inadequate by high, hydrocj^anic-acid content. This is probably due 

 to the need of glucosid Stimulation when the water supply be- 

 comes low. 



The character of the growth of the plant affects the distribution 



