394 Pflanzenkrankheiten. — Bacteriologie. — Bryophyten. 



the epidermal and corky layers, leaving in bad cases only one or 

 two instead of six or more layers; both old and young tubers are 

 subject to infection. Inoculation experiments show the inability of 

 this organism to invade the vine tissues of the host. 



Van der Lek (Wageningen). 



Kelley, W. P., Ni trification in semi-arid soils. (Journ. agr. 

 Research Washington. VII. p. 417—437. 1916.) 



In the writers investigations it has been shown that the amounts 

 of nitrate formed from dried blood, bone meal, or ammonium sul- 

 phate during four weeks' incubation varied enormously when difife- 

 rent concentrations were employed. This seems to be true in 

 regard both to the absolute amount of nitrate formed and the per- 

 centage of the nitrogen added that was nitrified. When equal 

 amounts of actual nitrogen were added it was found that the yields 

 of nitrate were quite similar, whether the nitrate had been derived 

 from dried blood, bone meal or ammonium sulphate. 



The effects produced by the addition of alkali salts varied 

 greatly when different concentrations of nitrogenous materials were 

 employed. In a given soil a concentration of 0.05 per cent ofsodium 

 carbonate was distinctly toxic to the nitrification of 1 per cent of 

 dried blood, while as high a concentration as 0.4 per cent produced 

 no effects on the nitrification of 0.1 per cent of dried blood. 



The results also show that widelj'- different conclusions may be 

 drawn from laboratory experiments when different periods of incu- 

 bation are used. The writer holds, that the methods now employed 

 by many students of nitrification, in which high concentrations of 

 nitrogenous materials are added and the nitrate determined at a 

 fixed interval of time, are not only unsatisfactory but that the re- 

 sults thus obtained are likel)?- to be more misleading than informing. 



The nitrate merely represents one of the end products formed; 

 and in the case of an organic substance the intermediate products 

 that are produced may, either directly or indirecth^ through the 

 effect upon other organisms, exert much influence upon the oxida- 

 tion of ammonia. In the presence of large amounts of materials it 

 is highly probable that the relations of the different groups of orga- 

 nisms present become greatly changed, with a consequent effect on 

 the oxidizing activity of the nitrifying organisnis. 



M. J. Sirks (Wageningen). 



Jensen, C, Danmarks Mosser, eller Beskrivelse af de i 

 Danmark med Färöerne fundne Bryofyter. I. Hepati- 

 cales, Anthocerotales og Sphagnales. Med talrige Figu- 

 rer. Udgivet paa Bekosting of Carlsberg fondet. (Gyl- 

 dendalske Boghandel, Nordisk Forlag, Kjöbenhavn, Kristiania. 

 317 pp. 34 Figurentaf. 1915.) 



Eine monographische Bearbeitung der Lebermoose und Torf- 

 moose Dänemarks (inklusive Bornholm und den Färöer) aus 

 der Hand des ersten Bryologen des Gebietes. 176 Lebermoose und 

 30 Torfmoose sind genannt und eingehend bearbeitet. Sein Leber- 

 moossystem ist folgendes: 



Familie I. Marchantiaceae. Unterf. 1. Riccieae, 2. Marchantieae. 

 Familie Tl. Jungermaniaceae. 



Gruppe A. ./. anacrogynae Leitg. (Unterfamilien: Fossombro- 

 nieae, Scalicae, Riccardieae, Mets^erieae). 



