4 i2 SCIENCE PROGRESS 



of the plant, and (4) the water-supplying power of the soil. 

 In the quantitative study of these controlling conditions, which 

 is absolutely necessary, the porous-cup atmometer, the radio 

 atmometer, the auto-irrigator have now been devised and per- 

 fected mostly in Livingston's Laboratory, while the method of 

 relative transpiration, the cobalt chloride paper method, and 

 soil osmometers have been employed, studied and modified. 



With regard to the inorganic salt relations of plants, Living- 

 ston has turned his attention to water culture and sand culture. 

 Both in his laboratory and elsewhere the whole question of 

 water culture technique has come recently under a rigorous 

 review. Lastly, " climate " has been analysed in its effect 

 upon growth, and in an interesting series of papers an attempt 

 has been made to work out a series of Climatic Indices for 

 growth over the whole of the United States. They are based on 

 reasonable approximations derived from meteorological data and 

 on quantitative standard physiological experiments on growth- 

 rates (Phys. Researches, 1916, vol. i., Nos. 8 and 9). 



Among further American publications which indicate 

 the modern tendency towards a new outlook in plant phy- 

 siology, the following must be referred to : Plants as a 

 Physical System, by L. J. Briggs (Joitrn. Washington Acad. 

 Sci. 191 7, 7, p. 89) ; Imbibition and Growth, by MacDougal 

 & Spoehr (Proc. American Phil. Soc. 191 7) ; and A Quarter- 

 century of Growth in Plant Physiology, by B. E. Livingston (The 

 Plant World, 191 7, 20, p. 1— 1 5). Under the heading of general 

 outlook certain publications in this country also are of 

 importance — e.g. Carbon Assimilation, by Ingvar Jorgensen 

 and Walter Stiles (William Wesley & Son, 191 7) ; Soil Condi- 

 tions and Plant Growth, by E. J. Russell (Third Edition, London ; 

 Longmans, 191 7) and Analysis of Agricultural Yield. III. The 

 Influence of Natural Environmental Factors upon the Yield 

 of Egyptian Cotton, by W. L. Balls (Phil. Trans. 191 7, 208, 

 B., and also Parts I. and II. Phil. Trans. B. 1915). In 

 Dr. Balls' work, devoted to a single crop over a span of years 

 and to an experimental analysis of the conditions con- 

 trolling its growth and production throughout its life, we 

 come at once into the presence of the new aspect of plant 

 physiology, to which I have alluded as about to emerge, and 

 which may be called the Science of the Living Plant. The 

 results obtained do not fail to impress the reader. Amongst 



