322 EXPEEIMENT STATION EECOED. 



liable to vary within somewhat wide limits, and (2) soils in which the soil 

 solution is poor in mineral substances and shows a relatively low and usually 

 also a relatively constant concentration. The roots or other absorbing organs 

 in contact with a soil solution of the first type are subject to high osmotic pressure, 

 which is moreover very variable, so that the plant must use such means of 

 regulation as it possesses in order to guard against the differences in tonicity 

 of the solution around its absorbing surface. In plants growing in a soil 

 solution of the second type the osmotic pressure around the absorbing surface 

 is very low, and its relative constancy enables the plant to dispense with the 

 regulatory mechanisms necessary for those growing in a more concentrated 

 solution." • 



A list of Gola's papers bearing on the subject is appended. 



The nature and methods of extraction of the soil solution, W. Stiles and 

 I. J0BGENSEN {Jour. Ecologi), 2 (19 lit). No. J^, pp. 245-250). — Results obtained 

 by different experimenters using different methods in investigating the actual 

 nutrient medium of plants by isolating and analyzing the soil solution are 

 briefly reviewed. 



It is thought that the investigation of the composition of soil water marks 

 a great advance in soil investigations. " However, the complex character of 

 the soil must not be forgotten, and it is especially necessary to remember that 

 the presence of colloidal substances (hydrosols and hydrogels) will naturally 

 alter the conditions of things." 



It is also thought that in extracting the soil solution the relations between 

 the crystalloids and colloids of the soil will suffer disturbance which will 

 result in a corresponding difference betw^eeu the actual soil solution and that 

 obtained by extraction. It is concluded, therefore, that the advance along 

 such lines " must depend veiy largely on further investigations into soil 

 physics." 



A list of references to related literature is appended. 



The difficulty with which soils and finely pulverized substances generally 

 are moistened, P. Ehrenberg and K. Schtjltze (Kolloi-d Ztschr., 15 (1914), 

 No. 5, pp. 183-192, fig. 1). — The authors briefly review the work of others bear- 

 ing on the subject, and report experiments with pulverized peat and lampblack, 

 from the results of which they conclude that the difiiculty of moistening lamp- 

 black, peat, and soil in the pulverized condition is due to the adsorption of air 

 and not to waiy or resinous coverings on the particles. 



The ground water, E. Grohmann {Jour. Landw., 62 {1914), No. 2, pp. 121- 

 123, figs. 2). — This article deals with the relations between precipitation, water 

 level in rivers, and ground-water level, with particular reference to the Elbe 

 River district in the neighborhood of Dresden. 



The results of several years' observations in this district show a marked in- 

 fluence of the precipitation on the ground-water level, which is, however, less 

 marked with the heaviest and the lightest rainfall in a given time than with 

 the rainfall of medium intensity, and less the lower the atmospheric humidity. 



The low ground-water level and Elbe River level in the district during the 

 past ten years, in spite of the heavy precipitations, is attributed to smaller 

 water absorbing and retaining powers of the soil caused by the kind of cultiva- 

 tion practiced. 



"Water movement in peat, H. J. Franklin {Massachusetts 8ta. Bui. 160 

 {1915), pp. 113-115). — Observations made, by means of test holes, on the move- 

 ment of water in the peat soil of the cranberry bog at the substation at Ware- 

 ham, Mass., indicated that if conditions in this bog are representative, the 

 horizontal movement of water through the peat of cranberry bogs is very rapid. 



