424 EXPERIMENT STATION RECORD. 



four principal divisions treated are soil bacteriologj', dairy bacteriology, the 

 bacteriology of the diseases of animals, and the bacteriology of foods. 



A biologic and taxonomic study of the genus Gymnosporangium, F. D. 

 Kern (Bui. N. Y. Bot. Gard., 7 (1911), No. 26, pp. 391-J,9.',, pis. 11, figs. 36).— The 

 results of a study begun at the Indiana Station in 1906 on the biology and 

 taxonomy of the genus Gymnosporangium are given. Preliminary notes on some 

 of the phases of the investigation have appeared previously (E. S. R., 19, p. 754; 

 20, p. 453; 23, p. 354). 



The author recognizes 40 species of the fungus, all of which are described at 

 length. Under the biological studies accounts are given of experimental investi- 

 gations on the life histories of different species of the fungus. Cultures were 

 made of 26 species and in IS they were successful. Of this number 9 were 

 cultivated for the first time and their alternate hosts demonstrated, the others 

 confirming previous reports. 



The economic importance of the species is discussed, especially those whose 

 secidial forms occur on such trees as the apple, pear, and quince. The methods 

 of control that have been suggested are reviewed, and the author points out some 

 of the difficulties attending spraying by reason of the prolonged season of the 

 maturing of the teleutospores. The planting of resistant varieties of apples, 

 pears, etc., is thought to offer promising results. 



Natural history, morphology, and cytology of Azotobacter chroococcuin, 

 A. Prazmowski (Centbl. Bakt. [etc.], 2. AM., 33 (1912), No. 11-U, pp. 

 292-305). — This is a somewhat detailed biological study of this dimorphic 

 schizomycete. 



It is stated that morphologically it presents itself in its first or vegetative 

 stage as a bacterium, in the fruiting stage as a micrococcus. Under certain 

 circumstances it resembles a ciliated free-moving fission fungus. The division 

 of the nucleus marlvs the first step in cell division. In the resting stage the 

 nucleus assumes a globular form, having a strongly refractive nucleolus, with 

 clearly differentiated bounding layer. The individuality of the nucleus appears 

 to be practically lost at times owing to its relations to the cytoplasm. The 

 so-called sarcina forms are said to be morphologically and physiologically 

 similar to the endogenous spores of other bacteria, in particular Bacillus 

 biitschlii. 



The physiology of denitrifying bacteria, H. von Caron (Centbl. Bakt. [etc.], 

 2. Abt., 33 (1912), No. 1-6, pp. 62-116).— This is an account of the author's 

 studies in extension of the work of Koch and Pettit (E. S. R., 23, p. 123), 

 employing cultures in soil of 3 common denitrifying bacteria, viz, Bacterium 

 Jiartlebi, Bacillus pyocyancu^, and Bacterium fluoresccns Uquefaciens. The in- 

 vestigations relate to the requirement and utilization of food and energy 

 materials by these bacteria in denitrification and the influence of atmospheric 

 oxygen in that process. The principal conclusions announced are as follows : 



Dextrose is a most suitable source of energy for nitrate reduction. So is 

 fresh straw ; but in rotting this loses much of its available carbon, so that 

 compost seldom shows much loss of nitrates by bacterial activity. Cellulose 

 may also serve as a source of energy in mixed cultures but in less degree. 

 Other sources of energy of varying availability are mentioned. The addition 

 of nitrogen increases the rate of denitrification, and this rises toward a maxi- 

 mum of intensity per unit of energy used. 



Investigations in the presence of hydrogen tend to confirm the view that 

 denitrifying bacteria are responsible for the loss of nitrates observed to occur 

 in the presence of a source of energy and of nitrates with exclusion of air. 

 The hydrogen is said to play here the role of a too high water content in the 

 soil ; whence it is inferred that any means of excluding air in soils may lead tp 



