1917] AGRICULTURAL BOTANY. 527 



proportions in wlilch tliey may be present around smelters ; whether they may 

 be carried down to crops by water ; whether they may prove to be permanently 

 or temporarily stimulating to plants ; and whether potassium aluminum sul- 

 phate can possess any value as a stimulant or as a source of potash. This work 

 is herein described and its results are discussed in some detail, and some com- 

 parisons are shown with findings of other investigators. 



The effect of various concentrations of the several compounds employed in 

 connection with the different soils are indicated in connection with the growth 

 attained by grain, straw, or roots. Stimulation usually attended the use of low 

 and, in some cases, rather high concentrations. 



Results are given regarding the effects of the salts on the nitrogen content of 

 the grain, the nitrifying powers of the soil, and the amounts of copper and zinc 

 taken up. Correlations are noted between some of these factors and the yields 

 of dry matter. Some theoretical and practical phases of the smelter question 

 are discussed, and evidence is cited to show that the solids of smelter waste are 

 not a menace to agriculture. 



Some effects of salt-treated soils on absorption by seeds, W. F. Geuicke 

 (Soil ScL, 3 {1911), No. 3, pp. 271-278).— The work above noted having raised 

 the question whether, owing to absorption, an increase would occur in the weight 

 of good viable seeds planted in soils containing solutions of certain toxic salts, 

 the author has carefully studied the behavior in this respect of the seeds of 

 several common economic plants. 



It was found that smaller applications of copper sulphate to soil increased, 

 and larger additions decreased, the absorption of water by bean and barley 

 seeds. Small applications of sodium carbonate to soils increased the weight of 

 bean, barley, and maize through increased absorption. Small applications of 

 sodium chlorid decreased water absorption by all of these seeds. 



Certain effects under irrig'ation of copper compounds upon crops, R. H. 

 Forbes [Univ. Cal. Pubs. Ayr. Sd., 1 {1917), No. 12, pp. 395-^9^, pis. 4, figs. 

 16). — Investigations are reported which show that as a direct effect of the 

 Clifton-Morenci mining operations in Arizona, copper is distributed throughout 

 the water supplies, soils, and the vegetable and animal life of an underlying 

 irrigated district. 



" Smaller amounts of copper are found elsewhere in the State where the 

 drainage basin includes mining operations or ore-bearing areas. Individual 

 plants grown in water cultures or in soil containing copper show a compara- 

 tively small, and probably not injurious accumulation of copper in the aerial 

 portions of the plants, but the root systems, carefully cleansed of externally 

 adhering copper, contain relatively great amounts. Copper in root systems, 

 a« shown by the biuret test, is largely in combination with plant proteids, 

 especially at the growing points of root systems and near vicinity. . . . Con- 

 ditions favoring toxicity of copper compounds are the presence of carbon 

 dioxid and certain soluble salts which assist in forming copper solutions that 

 come into contact with plant roots ; coarse, sandy soils favoring free access 

 of copper solutions to plant roots and minimizing the withdrawal of copper 

 from solution by adsorption ; and the presence of copper in the form of the 

 more soluble precipitated carbonate. . . . 



" Conditions opposing toxicity of copper compounds are the presence of copper 

 in the form of chrysocolla and chalcocite ; adsorption through contact with finely 

 divided soil particles ; reactions with carbonates, silicates, and organic matter 

 tending to precipitate copper from its solutions ; the presence of certain soluble 

 salts in the soil that overcome toxic action ; and increased resistance of old 

 plant roots. The stimulation by copper of vegetative growth in pot and water 



