SOILS FERTILIZERS. 515 



The author, therefore, couchides that a 2 per cent solution of citric acid is the 

 most reliable solvent for determining the readily soluble mineral constituents 

 of the soil in that, unlilie the other solvents used, it gives equally reliable 

 results for both phosphoric acid and potash. 



Determinations of the value of plant food constituents in soils and fer- 

 tilizers as dependent upon solubility, J. G. Maschhaupt and L. R. Sinnige 

 (Verslag. Landhouiolc. Onderzoelc. RijlcsJandiomcproefstat. [Netherlands], 

 1912, No. 11, pp. 19-73). — The author gives a critical review of investigations 

 by Mitscherlich on this subject (E. S. R., 19, pp. 110, 911), and reports the 

 results of his o\A'n studies of the solubility of different phosphates in saturated 

 water solutions of carbon dioxid and in citric acid (2 per cent) by single and 

 repeated extraction. 



The results showed that continued extraction with fresh quantities of the 

 solvents was a more reliable method of determining the solubility of the phos- 

 phates and their fertilizing value than a single extraction. The water solution 

 of carbon dioxid is preferred to citric acid on account of the fact that it is the 

 most important, although not the only, solvent at the disposal of the soil and 

 the plant roots, although the contention of Mitscherlich, that the action of carbon 

 dioxid solutions is similar to that of the roots in physiological processes of plant 

 growth, is not accepted. 



Remarks on absorptive saturated and unsaturated soils, A. Rindell {Sepa- 

 rate from PochcovTcdfcnie (Pedologie), 1912, No. 1, pp. 11). — This is a brief 

 critical discussion of the views of.Ramann and of Gedroits (E. S. R., 26. p. 30). 



The author holds that the classification of soils as absorptive saturated and 

 unsaturated is too indefinite to be of value, except as denoting whether a soil is 

 rich or poor in absorptive combined bases. The judging of the absorptive prop- 

 erties of soils by their chemical behavior toward neutral salt solutions is also 

 of no value without a knowledge of the kind of bases absorbed. 



The relation of evaporation to the water content of the soil at the time 

 of wilting, W. H. Brown {Plant World, 15 {1912), No. 6, i)p. 121-13',).— -Ex- 

 periments to determiiie the relation between the evaporating power of the air 

 and the percentage of water in the soil at the time of wilting of plants of 

 Martynia louisiana, Physalis angulata, Tropaeohim majus, and Vicia faba, are 

 reported. 



The plants were grown " first in the open, exposed to the direct rays of the 

 sun ; second, under a lath shelter ; third, in a room within a thick-walled adobe 

 house; fourth, in a glass chamber in the same room, the air in this chamber 

 being kept nearly saturated with moisture." The soil used was a mixture of 

 equal parts, by dry volume, of clay-loam and sand with a water-holding capacity 

 of 31.4 per cent of the weight of dry soil. 



The results of these studies showed that the percentage of soil moisture at 

 the time of wilting of the plants grown under the same conditions and in the 

 same soil varied " with the rate of evaporation at the time of wilting, provid- 

 ing, however that, in the case of altered conditions, the plant is not allowed 

 time enough under the new evaporation rate to become physiologically altered. 



" This residual moisture content of the soil at the time of wilting varies ac- 

 cording to the atmospheric conditions under which the plant has been grown and 

 appears to be increased by excessive soil temperatures." 



The moisture content of the soil at the time of wilting varied among the dif- 

 ferent plants " within but comparatively narrow limits for any given evaporat- 

 ing power of the air during the hour preceding wilting." 



Data and observations on the salt content of drainage waters of the pold- 

 ers of North Netherlands, A. D. Berkhout {Cultura, 24 {1912), No. 286, pp. 

 227-282, fig. 1). — Determinations were made of the sodium-chlorid content of 



