950 EXPERIMENT STATION RECORD. 



soils and its determination (see E. S. R., 17, p. 436), and the optimum temperature 

 for Azotobacter as compared with soil temperatures. 



The results, which are reported in detail, show that while there is no doubt as to 

 the power of Azotobacter to fix nitrogen under laboratory conditions, it is not certain 

 that this is a specific characteristic like the power of yeast to produce alcohol. It is 

 thought possible that when the organism is supplied with a large amount of organic 

 matter containing nitrogen its nitrogen-fixing power may be destroyed, and, like 

 yeasl when grown in peptone media, may show very different properties from those 

 ordinarily in evidence. 



The growth of Azotobacter in artificial media is not therefore to be considered 

 unique or typical. The mode of operation of the organism in the soil is very imper- 

 fectly understood and can not be thoroughly cleared up until more accurate methods 

 of determining the very small variations in nitrogen content of the soil which are 

 involved in studies of this kind are secured. Moreover, the temperature conditions 

 in laboratory cultures do not obtain in the natural soil, and therefore the optimum 

 conditions for activity of the organism are not always present. In view of the fact 

 that the life and the work of Azotobacter are still to a large extent unsolved problems, 

 the practical man is not warranted in expecting that Azotobacter fertilizing will in 

 the near future take the place to any extent of applications of nitrate of soda. 



Numerous references to the literature of the subject are given and the methods and 

 apparatus used in the experiments reported are described. 



The assimilation of free elementary nitrogen by micro-organisms, J. Vogel 

 | Cenlbl. Bald, [etc.'], 2. AbL, 15 (1905), Xos. 2-3, pp. 33-53; 4-6, pp. 174-188; 7-8, 

 j>j>. /15-227). — A review is given of the more important investigations on this sub- 

 ject, bringing out especially how chemical treatment of the soil and use of fertilizers 

 may retard or promote the activity of different groups of these organisms. A bibli- 

 ography of the subject containing 148 references is given. 



Nitrogen-fixing bacteria, T. W. Kirk (New Zeal. Dept. Agr. Ann. RpL, 13 ( 1905), 

 PI*. 343-346, pis. 3). — The history of investigation on this subject is briefly reviewed, 

 and experiments on beans, peas, vetches, and red clover with the inoculating material 

 prepared by this Department are reported. 



"The results proved (1) that on land which will already produce a good crop of 

 legumes the inoculation is of little benefit to the crop treated, but (2) it increases the 

 number of nodules on the roots and consequently the quantity of nitrogen left in the 

 soil for the benefit of a following crop, such as grain or roots, which have not the 

 power of providing nitrogen for themselves; (3) the inoculated seed invariably gave 

 better results than the inoculated soil." 



The relative merits of inoculation by means of infected soil and by pure cultures 

 are discussed and directions and precautions to be observed in the use of inoculating 

 material are given. 



Cooperative experiments with nodule-forming bacteria, F. (_\ Harrison and 

 B. Barlow (Ontario Agr. Col. and Expt. Farm Bui. 148, pp. 19, figs. 7).— This bulle- 

 tin contains brief statements regarding the history of the discovery of these organisms 

 and summarizes the results of tests made by farmers in different parts of Canada of 

 liquid cultures distributed by the Agricultural College at Guelph. 



The cultures were sent out in small bottles in such condition that all the farmer 

 had to do was to mix the contents of the bottle with a measured quantity of water 

 and then apply to his seed. Cultures for alfalfa, alsike clover, red clover, white 

 clover, soy beans, vetches, peas, and beans were distributed. Of the 134 reports 

 received. 91 showed benefit from inoculation, 40 no advantage, and 3 stated that the 

 organisms were already present in the soil. Extracts from the individual reports are 

 given as well as detailed directions for using the cultures. 



Tests of commercial cultures of nitrogen-fixing bacteria ( V. S. Dept. Agr., 

 Office Sec. Circ. 16, folio).— This circular calls attention briefly to the limitations of 



