BOOKS AND CURRENT LITERATURE 169 



deferred grazing restores and maintains the vegetation without the 

 loss of the forage crop. Since it prevents the accumulation of a large 

 amount of dry forage it at the same time lessens chances of fire. 

 Quadrats cropped at frequent intervals, compared with others cropped 

 only after seed production, would have further emphasized the advan- 

 tages of this system, since frequent cropping greatly reduces yield. 

 In the Wallowa Mountains one-fifth of the grazing season remains 

 after seed production and one-fifth of the land may be retained for 

 deferred grazing. It is desirable to practice delayed grazing for at 

 least two years in succession on each area in order to secure the best 

 results. 



The plant ecologist will find in this paper an excellent example of 

 the practical application of ecological methods to the problem of range 

 economy and will be amply repaid for a close inspection of the life his- 

 tory studies. The range man will find suggestions of practical value 

 and applicable with minor modifications to all regions in which there 

 is danger of depletion of the natural range. — H. L, Shantz. 



Physiological Balance in Nutrient Media. — The method of 

 water cultures has but recently been given attention with respect to 

 the control of the several factors involved, a consideration which will 

 be necessary to render the results obtained from it of far reaching 

 physiological importance to the subject of plant nutrition. Shive' 

 has recently made a distinct contribution to the development of this 

 method. 



The purpose of the investigation, as explained by the author, was 

 to develop a nutrient solution, as simple as possible, which should be 

 suitable for a control in future work with water cultures. By omitting 

 potassium nitrate from the salts employed in Knop's nutrient solution 

 there was obtained a new solution that retains all of the constituent 

 ions of the original. The three remaining salts (Ca(N03)., MgS04 and 

 KH2PO4) were employed by Shive in various different proportions and 

 in three different total concentrations, the latter being sub-optimal, 

 optimal, and supra-optimal with respect to the growth of young wheat 

 plants. These three concentrations had total osmotic pressures of 0.10, 

 1.75 and 4.00 atmospheres respectively, and the partial pressure due 

 to each salt was varied by increments of one-tenth of the total pres- 



1 Shive, J. W. A study of physiological balance in nutrient media. Physiol. 

 Res., 1: 327-397. 1915. 15 figures. 



