40 



BOOKS AND CURRENT LITERATURE 



very apt to allow words to pass which would not be chosen if writing 

 for a more restricted group of readers. While the general truths hold 

 as stated, the details are often in error, according to the usual use of 

 words, as when proteids are said to be "eliminated" in the seeds and 

 falling leaves of plants. The reviewer regrets to see so much effort 

 placed on a text covering a field which has been outgrown by its com- 

 ponent parts. Biology, like Microscopy, has developed into intensive 

 study, and can not be satisfactorily covered in a single text. 



Frederick H. Blodgett. 



Bacteria in Frozen Soil. — Work by Brown and Smith is in part a 

 confirmation of , that of Cohn relative to the existence of specific groups 

 of bacteria which are capable of living and rapidly multiplying in frozen 

 soils. 1 A seemingly plausible explanation for this condition is that the 

 films of hygroscopic water become more concentrated as the main bod}^ 

 of soil water freezes, thus depressing the freezing point so that the 

 hygroscopic moisture may remain uncongealed. Then, too, it is a well 

 known fact that the pressure exerted in holding the film around the 

 soil particles is sufficient to lower the freezing point of the hygroscopic 

 water below zero degrees Centigrade. The evidence which the authors 

 adduce indicates that frozen soils possess a much greater ammonifying 

 power than non-frozen soils. Frozen soils possess a weak nitrifying 

 power but a decided denitrifying power which diminishes as the cold 

 continues. There is, as the frozen period continues, an increase in the 

 nitrogen fixing power of frozen soils, the fixation being less, however, 

 than in the fall season. — Frederick A. Wolf. 



Evaporation in Illinois. — Gleason and Gates have published the 

 results of their study of relative evaporation in central Illinois.- The 

 plant associations investigated range from the "blowout" association in 

 loose sand to the mixed forest, which is the local climax of the uplands 

 about Havana. The results are represented in terms of an arbitrary 

 standard as follows: blowout 1.27-1.56, bunchgrass 1.04-1.18, beach 

 (along Illinois River) 0.93, black oak 0.55-0.66, willow 0.44-0.56, mixed 

 forest 0.29-0.36. The authors conclude that the difference in the 

 various associations is due principally to the nature of the vegetation. 



' Brown, P. E. and Smith, R. E.: Bacterial activities in frozen soils. Iowa 

 Agr. Exp. Sta. Res. Bull. 4: 159-184, 1912. 



* Gleason, H. A. and Gates, F. C.: A Comparison of the Rates of Evaporation 

 in Certain Associations in Central Illinois. Bot. Gaz. 53: 478^91, 1912. 



