172 BOTANICAL GAZETTE [February 



Gesell. 30:52-65, 293-305, 504-816. 191 2; Groves, J. F., Temperature and 

 life duration of seeds. Box. Gaz. 63:169-189. 1917. 



On oxygen relations of plants. — Shull, Charles A., The oxygen minimum 

 and the germination of Xanthium seeds. Box. Gaz. 52 : 453-477. 1911 ; Cannon, 

 W. A., and Free E. E., The ecological significance of soil aeration. Science 

 N.S. 45:178-180. 1917; LiviNGSXON, B. E., and Free, E. E., The effects of 

 deficient soil oxygen on the roots of higher plants. Article in " Contributions to 

 Plant Physiology." Johns Hopkins University. Reprint from Johns Hopkins 

 University Circular. March 19 17. 



The new edition deserves high praise for its comprehensive treatment and 

 impartial judgment on the modern developments in soil chemistry. The dis- 

 cussion on the use of dilute acids in soil analysis, based on the author's own work 

 in the Rothamsted laboratories, is the first contribution on this subject that has 

 forsaken empirical experimental methods and adopted a modern physico- 

 chemical procedure. The review of the highly controversial literature on soil 

 acidity is eminently fair. The attention of the reader is called to the following 

 recent papers, each of which contains an extensive bibliography: Chrisxensen, 

 H. R., Experiments in methods for determining the reaction of soils. Soil 

 Science 4: 1 15-178. 1917; Truog, E., Soil acidity. I. Its relation to the growth 

 of plants. Soil Science 5:169-195. 1918; Rice, F. E., and OsuGi, S., The 

 inversion of cane sugar by soils and allied substances and the nature of soil 

 acidity. Soil Science 5:333-358. 1918. 



The biological aspects of soil science are fully treated, including the author's 

 own interesting ideas on soil protozoa and partial sterilization. The reviewer 

 feels that Russell has been somewhat partial to his own views in not referring 

 to Sherman's studies. Sherman concludes, on the basis of his experiments, 

 that "no evidence has been obtained which indicates that the beneficial effect of 

 partial sterilization is due to the elimination of a biological factor which is 

 harmful to the bacteria." Bolley's interesting views on "Soil sanitation" 

 deserve mention in a chapter that bears such an all-inclusive title as "The 

 relationship between the micro-organic population of the soil and the growth of 

 plants." The following papers should be read in connection with the chapter: 

 Sherman, J. M., Studies on soil protozoa and their relation to the bacterial flora. 

 Jour. Bacteriology 1:35-66, 165-185. 1916; Kopeloff, N., and Coleman, 

 D. A., A review of investigations in soil protozoa and soil sterilization. Soil 

 Science 3:197-269. 1917; Bolley, H. L., Wheat-soil troubles, causes of soil 

 sickness, etc. Bull. 107. N.D.Agric. Exper. Sta. 1913; Bolley, H. L., Con- 

 servation of the purity of soils in cereal cropping. Science N.S. 32:529-541. 

 1910; Bolley, H. L., Cereal cropping: sanitation, a new basis for crop rotation, 

 manuring, tillage, and seed selection. Science N.S. 38:249-259. 1913; Hop- 

 kins, C. G., The bread supply. Science N.S. 38:479-481. 1913. 



Keen's mathematical studies on the retention of water by soil are amply 

 discussed, but no mention is made of Shull's even more important contribution 

 to the problem of the wilting coefficient. The reader is therefore referred to the 



