528 EXPERIMENT STATIOK RECORD. [Vol.37 



cultures has been observed. Stimulated growth of crops under field conditions 

 is a possibility. 



" Pot cultures may be used for comparative determinations of toxic effects 

 upon plants of copper in soils, if conducted under rigidly uniform conditions. 

 The copper content and the physiological response to copper of such material 

 will be much greater than for similar cultures grown under plat or field con- 

 ditions. Copper injury in field soils containing doubtfully toxic amounts of 

 copper may be diagnosed by a combination of symptoms. Facts which indicate 

 such injury in a soil containing 0.1 per cent of copper (more or less) are 

 yellow tops (for winter gi-ains) in absence of other conditions that cause 

 yellow tops, crinkly root systems (in absence of excessive amounts of alkali 

 salts), and a high copper content in dry matter of root systems. Combined 

 evidence of this character, which may be observed in the district studied, in- 

 dicates toxic copper effects. 



" Field observations before and following the exclu.sion of tailings from the 

 irrigating water supply indicate that conditions in the district studied are 

 gradually improving, due to the cultivation of alfalfa and to the incorporation 

 of river sediments with accumulations of tailings. Noticeable toxic effects lu 

 the field exist only where the roots of young, growing crops are exposed to 

 surface soils containing maximum amounts of copper. The general tendency 

 in the district is probably toward decreasing rather than increasing percentages 

 of copper in irrigated soils." 



Methods of experimental procedure are described. 



Fifty-seven references to literature bearing on the subject are appended. 



Protection against pollution of waters and smoke and dust injury to agri- 

 culture and forestry in Austria, J. Stoklasa (ilitt. Verhandl. Landiv. Rats 

 [Aiistria], It (191S), pp. 141-163). — Besides discussing reports on emanations 

 from such sources as furnaces and chemical works in different countries during 

 some years past, the author deals more specifically with several phases of water 

 pollution and with such emanations as smoke, dust, and gases, and the injury 

 done thereby to plants. 



One of the most important of the injurious factors is sulphuric acid, which 

 is discussed as regards its effects, both direct and indirect. The action on the 

 leaves is far-reaching as regards results, though not necessarily apparent in the 

 early stages of the processes. The effects of some other components are 

 somewhat systematically discussed. 



FIELD CROPS. 



Field experiments and compensating calculations, R. Leidner {LandiC. 

 Jahrb., 40 {1916), Ko. 1, pp. 105-135, figs. 3). — The author reviews experimental 

 work by Riimker, Rodewald, Hummel, Remy, Ehrenberg, Pfeiffer, Mitscherlich, 

 and others in an attempt to ascertain those methods that secure the greatest 

 accuracy in field experiments. Considerable data are given and discussed. 



The general conclusion is drawn that the most suitable means for conducting 

 field experiments has not yet been found, although the transition from the early 

 two-plat system to the newer method of using many small control plats and the 

 detailed statement of the technical and mathematical phases of the subject 

 studied are advances in the right direction. A more careful selection of 

 experimental field plats and increased attention to all the details of experi- 

 mental work are natural consequences following such a practice. 



[The experimental error in field tests], V. G. Batyrenko (Zhur. Opyin. 

 Agron. (Jour. Agr. Expt), 11 (1916), No. 2, pp. 99-121).— The author discusses 

 the factors involved in experimental errors in field tests, with special reference 



