NOTES AND ABSTEACTS. 



655 



It is shown that in soil containing three times more water than its 

 average air-dry condition, nitrification is at a standstill. The optimum 

 water content for nitrification is between 14 and 18 per cent. Summer 

 working of fallow land so as to retain moisture may thus have an 

 important result in the production of nitrates. — F. J . G. 



Nitpogren-fixation in Soils in Colorado. By W. G. Sackett 

 [IJ.S.A. Exp. Stn., Colorado, Bull 179; June 1911; figs.)— A^oio- 

 hacter Chroococcum appears to be the chief nitrogen fixing organism 

 in the Colorado soils. It develops a dark brown pigment in the 

 presence of nitrates, imparting that tint to the soil, nitrites causing 

 its production to a less degree. Nitrification goes on in all the soils 

 investigated except where limited by excessive soil moisture. 



F. J. G. 



Nitpog'en, Fixation of, in Colorado Soils. By W. P. Headden 

 (U.S.A. Exp. Stn., Colorado, Bull. 178; June 1911; figs.).~This is a 

 chemical study of the rate of nitrogen fixation in some soils of Colorado 

 and deals with the rate of nitrification under different conditions of 

 moisture. — F. J. G. 



Nitrogren-Gatheringr Plants. By Karl F. Kellerman {U.S.A. 

 Dep. Agr. Year Book, pp. 213-218, 1910; illustrated). —It is now 

 common property that leguminous plants have nitrogen-fixing nodules 

 upon their roots, but probably not so generally known that some non- 

 leguminous plants also have this characteristic, among them being the 

 Alder, Geanothus americanus, Elaeagnus argentea, Gomptonia pere- 

 grina, and several representatives of the Cycadaceae. 



The root-nodules are as typical in general character for each kind 

 of plant as their other points of differentiation — such as the shape of 

 their leaves, or the arrangement of these on the stem. The spherical 

 nodule is probably the most common form. — G. H. L. 



Olive Propagation. By A. E. de Mazi6res, J. Chapelle, and 

 J. Euby (Rev. Hort. d'Alg. p. 107; April 1912).— Two articles on 

 propagation of olives by seed, by cuttings, by layering, and by various 

 forms of grafting and budding. Some practices peculiar to Spain and 

 Tunis are described, and generally the particular conditions under 

 which each method is most suitable are pointed out. — M. L. H. 



Onion Seed and Sets, Home Production of. By W. E. 



Beattie (U.S.A. Dep. Agr., Farmers' Bull. 434; 1911').— Farmers 

 generally are returning to the custom of growing their own onion seed, 

 which is well, on the v/hole, as they can practise selection better than 

 the commercial growers ; and also, carefully grown seed planted in the 

 same general locality will give better results than seed brought from 

 a distance. This is especially true in northern localities, where the 

 season of growth is short, as southern -grown seed requires a longer 

 season for its maturity. 



