AGRICULTURE AND RURAL ECONOMY. 549 



cum, Aspergillus niger, 3ucor mucedo and racemosus, and 

 3fycoderma vini and aceti. These organisms were grown 

 in media supplying ammonia or organic nitrogen. No for- 

 mation of nitric acid could be detected. Instead of oxidiz- 

 ing nitrogen, these organisms were found to feed upon nitric 

 acid as well as on ammonia. The consumption of nitrogen 

 compounds by their growths tallies well with the old observa- 

 tion that mould in nitre beds is prejudicial to the formation 

 of saltpetre. There is apparently no loss of nitrogen during 

 the growth of mould until fructification commences. Rapid 

 combustion of organic matter then takes place, and free ni- 

 trogen is evolved. At the same time ammonia may be pro- 

 duced. It would seem, then, that these organisms, which 

 are recognized as active oxidizers, are not the ones that pro- 

 duce nitrification ( Comj)tes Hendus, lxxxvi., 892). 



To resume, it seems clear that the oxidation of nitrogen 

 compounds in the soil with nitric acid is due, at least in part, 

 to living organisms, organized ferments, but that the organ- 

 isms that do this work are not the ones that cause alcoholic, 

 acetic, and other familiar kinds of fermentation. 



Agency of Metallic Oxides in the Formation of Nitrates. 



Reichardt cites and repeats some experiments by Hiinefeld 

 on the capability of certain oxides to cause the oxidation of 

 free nitrogen, and concludes that this power is possessed not 

 only by the higher oxides of manganese, as has been previ- 

 ously observed, but by magnesia even in the form of the com- 

 mon basic carbonate. He considers this of high importance 

 in explaining the formation of nitrates in the soil (Jour.f. 

 Landw. , 1 8 7 8, 1 6 7) . 



IV. THE PLANT. 



CHEMISTRY AND VEGETABLE PHYSIOLOGY. 



Though the subject of vegetable physiology belongs prop- 

 erly to botany, brief reference to a few of the more interest- 

 ing features of plant-growth may not be out of place here. 



In a lecture before the London Chemical Society, on the 

 Chemical Aspect of Vegetable Physiology, Vines has dis- 

 cussed the conclusions arrived at by chemists and vegetable 

 physiologists concerning some of the substances that com- 

 pose the tissues and are found in the cells of plants, the 



