AGRICULTURAL BOTANY. 325 



Some bacteriolo^cal studies of old soils, L. T. Sharp (Ptant World, 16 

 (191S), No. If, pp. 101-115). — The author describes a bacteriologrical examina- 

 tion of soil samples tliat had been kept tightly stoppered for from 25 to 33 

 years in the soil laboratory of the University of California. The investigation 

 included not only a study of the number of organisms present, but also their 

 physiological characteristics as shovpn by their ammonification, nitrification, 

 and nitrogen fixation powers. The soil samples represented a variety of types, 

 from heavy adobe to light red sandy soils, together with samples containing 

 varying quantities of alkali, so that the diversity in the samples, it is believed, 

 permits of a wide application of the facts obtained. 



It was found that soils free from excessive alkali salts retained from 75,000 

 to 570,000 organisms per gram after 30 years drying under room conditions. 

 Alkali soils under simUar conditions contained from 5.000 to 60,000 organisms 

 per gram. The ammonification flora were found most resistant to drying, being 

 especially strong in the alkali soils. The nitrification occurred feebly in 2 soils 

 but was permanently destroyed in 7 others. Azotobacter was entirely absent in 

 all but one sample, though the nitrogen fixation power of the soils was well 

 maintained by other organisms. There seemed to be no relation between the 

 numbers and physiological efficiency of the organisms present. It is believed 

 that the persistency of these organisms under dry conditions and their renewed 

 activity in the presence of sufiicient moisture is agriculturally important. Soil 

 is believed to exhibit a protective function toward the lower forms of plant life 

 under adverse conditions. 



The activity of bacteria in forest soils, "W. Migcla {Forstw. Centbl., n. ser., 

 35 (1913), No. Ji, pp. 161-169). — This is an account of several investigations 

 with decoctions made from fallen leaves and pine straw, supplied with 0.5 per 

 cent peptone and 0.5 per cent sugar, rendered neutral or slightly alkaline where 

 necessary, and inoculated with cultivated soil, much richer in bacteria than 

 was the forest soil. 



It was found that the growth of bacteria, which was rapid in some cases, was 

 finally checked by the development of several acids, attributed to the activity 

 of the bacteria themselves. It is thought that in decaying forest leaves these 

 acid products are subject to the washing action of rain, which thus favors the 

 limited bacterial action observed at and near the surface of wood soils. The 

 decomposition observable in these upper layers is attributed almost wholly to 

 fungi which are there relatively active. Investigations concerning the possible 

 role played by thermophilic bacteria gave but slight results, possibly on account 

 of the rain and coolness prevalent in the summer of 1912. Further investiga- 

 tions of anaerobic bacteria in this connection are contemplated. 



The phenomena of fermentation as acts of digestion. — New evidence from 

 the study of denitrification in plants, P. Maz£ (Ann. Ijist. Pasteur, 25 (1911), 

 Nos. 4, pp. 289-312; 5, pp. 369-391, figs. 4; ahs. in Bot. Centbl, 122 (1913), 

 No. 10, pp. 207, 208). — The author's studies are claimed to lead to the following 

 conclusions : 



The addition of nitrates to cultures of denitrifying bacteria does not alter 

 the character of the fermentation. Any resulting change in proportion is 

 attributable to the paralyzing efi'ect of the nitric acid formed on the develop- 

 ment of the organisms. The reduction of nitrates by anaerobic bacteria (not 

 all of which are denitrificants) is due to the disengagement of hydrogen. This 

 reduction of nitrates is not necessarily associated with the formation of 

 ammonia. The more active denitrificants are the better adapted to the assimi- 

 lation of nitric acid. Higher plants reduce nitrates with formation of nitric 

 acid and its gaseous derivatives. In a 0.1 per cent solution of potassium 



