170 BOOKS AND CURRENT LITERATURE 



sure, by a method similar to that employed in the earher work of the 

 reviewer.^ Thirty-six cultures thus constituted a series for each of 

 the three concentrations. Data of yields and physiological disturb- 

 ances apparent to the eye have been analyzed by Shive inconsiderable 

 detail and the results are well summarized in graphic form. There is 

 no doubt that Shive's best three-salt solution is eminently suited to 

 serve as a present criterion of efficiency for nutrient solutions employed 

 with the optimal concentration with which he worked, in the case of 

 wheat. Data of yields from a number of solutions described in the 

 literature and used by him simultaneously and at a uniform concen- 

 tration establish this fact. 



Among the several conclusions derived from this investigation the 

 most important relate to the physiological balance of the constituent 

 ions. The most significant is to the effect that the value of a given 

 ratio of salts varies with the total osmotic pressure, or salt concentra- 

 tion, of the solution, A serious attempt to analyze in detail the ionic 

 ratios involved in the many solutions employed developed the further 

 conclusion that no single ratio of ions determines the effect of a given 

 ratio of salts, but that the effect depends upon the mterbalance of all 

 the ions present. Attention is thus directed emphatically to the im- 

 portance of considering the serious disturbance of physiological effici- 

 ency which may result whenever an additional chemical element, or 

 ion, is added to any given nutrient solution. 



In an effort to subject all the cultures of a series to uniform aerial 

 environmental conditions to the fullest possible extent they were sup- 

 ported upon constantly rotating tables. Further data are given which 

 support previous investigations with respect to a direct relation between 

 transpiration and growth of wheat and an inverse relation between 

 both transpu'ation and water requirement on the one hand and total 

 concentration of the nutrient solution upon the other hand. 



It is no small task to digest and summarize such a complex of data 

 as have been treated in Shive's paper. The author is to be especially 

 commended for the helpful methods of tabulation and illustration 

 which he has employed. The field covered by the investigation is one 

 of prime interest to physiologists on account of the great importance of 

 the relation of soil nutrients to plant growth. The method here em- 

 ployed should lead to further experimental control and analysis of the 



2 Tottingham, William E. A quantitative chemical and physiological study 

 of nutrient solutions for plant cultures. Physiol. Res. 1: 133-245. 1914. 



