AGEICULTUEAL BOTANY. 423 



It is believed that carbon dioxld formation in a soil is a reliable measure of 

 tbe bacterial activity therein and an index of changes unfavorable thereto. By 

 measuring such formation of carbon dioxid it was possible to determine opti- 

 mum moisture content as regards bacterial activity, this varying from 16 to 37 

 per cent. It was found possible also thereby to ascertain the optimum propor- 

 tions for addition of such substances as lime or superphosphate in order to 

 promote the decomposition of green manures, oil cake, etc., also to direct prac- 

 tice to the advantageous control of moisture content of soils. 



The investigations seemed to show that the high relative rate of bacterial 

 activity and consequent biologic changes taking place in Indian soils are due to 

 the higher temperature (25 to 30° C.) during much of the year, as compared 

 with that in European soils, averaging 15 to 18°. At the lower temperature 

 ammonification and nitrification go on at about equal rates. At the higher 

 temperature the former proceeds much more rapidly and may produce so high 

 a concentration of ammonia in the soil water as to diminish or inhibit nitrifica- 

 tion, so that much nitrogen may be lost in the form of ammonia. These facts 

 are considered to have important bearings upon practical operations in 

 agriculture. 



It appears also that when intense bacterial activity is present in soils, 

 nitrates are reduced without occurrence of anaerobic conditions, being utilized 

 presumably as a nitrogen source by the bacteria. At Pusa, the optimum mois- 

 ture content is 16 per cent while general bacterial action is intense up to 25 per 

 cent, and at the latter humidity rapid reversion of nitrate to the protein 

 form takes place. This is thought to explain in part the fact that at Pusa and 

 in the Punjab excessive moisture resulted in nitrogen starvation of the wheat 

 crop. The formation and effects of bacteriotoxins are still under investigation, 

 as are also the effects of green manuring upon soil conditions and subsequent 

 crops. 



A bacterial disease of tobacco at Rangpur was found to be due to a strain of 

 Bacillus solanacearum, which was pathogenic also to eggplant, tomato. Datura, 

 and potato. The parasitism seemed weak originally, but was found capable of 

 cultivation to a high degree of virulence, from which fact it is thought best to 

 leave no plants for a second cutting in the infected areas. A bacterial disease 

 of wheat in Punjab, locally known as tannan or tandu, was found to be due to 

 an attack of a bacillus closely resembling Pseudomonas hyacinthi. This, how- 

 ever, is thought to be confined to small badly drained areas and of little eco- 

 nomic importiince imder proper cultivation. 



Studies with sterile cultures of hig'her plants, I. Schuxow (Ber. Dent. Bot. 

 Gesell., 31 (1913), No. 3, pp. 97-121, figs. 2). — In continuance of previous work 

 (E. S. R., 27, p. 634; 28, p. 225), the author reports that his investigations con- 

 firmed the influence of micro-organisms on the solution of organic phosphates. 



It is stated that peas and corn assimilated the phosphoric acid of pliytin but 

 not that of lecithin, also that the roots of both peas and corn separated reducing 

 and nonreducing sugar and malic acid, ammonium nitrate proving a better 

 source of nitrogen than calcium nitrate. Young plants utilized at first the 

 nitrogen from the ammonium radical of ammonium nitrate in the higher degree, 

 but later that from the nitrate radical in about equal degree, and still later 

 in the higher degree. This change in nitrogen source corresponded to a change 

 in the physiological character of the solution from acidity at first, through 

 neutrality, to alkalinity. * The physiological acidity of ammonium nitrate is 

 thought to play an important part in the solution and utilization by higher 

 plants of the phosphates which are insoluble in water. 



The prevalence of Bacillus radicicola in soil, K. F. Kellebman and L. T. 

 Leonaed (Science, n. ser., SS (1913), No. 968, pp. 95-98). — The authors report 

 8297°— No. 5—13 3 



