14 EXPERIMENT STATION RECORD. 



several different lines of evidence. (1) Pure water is uniformly better suited 

 to growing wheat seedlings for short periods than is the soil extract from the 

 poor soils. It is also better suited to the preparation of a nutrient solution. (2) 

 Finely divided, insoluble solids, when shaken with these extracts and then 

 removed by filtering, generally produce a great improvement. Since the only 

 conceivable way in which these can act is through their absorbing action, it is 

 to be supposed that they owe their effect to the fact that they absorb, and thus 

 remove from solution the toxic bodies existing in the extract. (3) The extracts 

 of these soils are benefited by nutrient salts, especially sodium nitrate, but it is 

 pointed out that these may be effective through some other means than the 

 phenomena of nutrition. Certain nonnutrients, such as sodium ehlorld, pyro- 

 gallol, and tannic acid, produce marlced beneficial results. Since these can not 

 act directly through nutrition, they must have some action either upon the toxic 

 bodies, making them nontoxic, or upon the plant, causing it to become more or 

 less immune to the toxic bodies. (4) The same chemicals have similar effects 

 when added to the soil itself. Here the action is more difficult of analysis, but it 

 seems probable that the chemicals act in the same general way as in the aqueous 

 extract. 



" The toxic substances here considered appear to be but slightly soluble in 

 water ; they are sometimes volatile with steam and sometimes not ; the soil 

 extracts containing them are usually more or less acid in reaction, but the 

 acidity is not in itself the cause of their deleterious action ; they are probably 

 organic and are absorbed by finely divided solids. 



" Evidence is pi-esented to the effect that injurious materials similar to the 

 ones existing in the soils are produced by the growth of wheat in water or sand 

 cultures. Bodies of similar toxic action are also exuded from soaking wheat 

 seeds, and, in some cases at least, may be washed from the bark and leaves of 

 trees." 



The experiments on the effect of stable manure and green manure on the 

 toxicity of soils were made on the Takoma lawn soil and on the subsoil from 

 the Department grounds. The results indicate that the beneficial effects ob- 

 tained from the use of stable manure and green manure " are probably, in large 

 part, due to the oi'ganic matters therein contained rather than to the salts car- 

 ried into the soil l)y such treatments. That the organic matter is directly of use 

 to plants as nutrient material is not probable ; it appears to be beneficial largely 

 through some action upon the soil constituents." It is suggested that the bene- 

 ficial effects are due to action of the organic matter of the manures in so altering 

 the toxic substances as to render them harmless. 



In the course of the experiments referred to above it was found that distilled 

 water, as ordinarily prepared and stored in the laboratory, has a decided toxic 

 action on young plants. Simple redistillation in glass is not sufficient to correct 

 this toxicity. It was found, however, that by shaking the water with finely 

 divided and thoroughly clean carbon black of precipitated ferric hydrate and 

 filtering, the quality of the water in this respect was very greatly improved. 



The paraffined wire basket method of soil investigation of the Bureau of 

 Soils, United States Department of Agriculture, C. E. Thokne {Ohio Sta. Circ. 

 70, pp. 7). — The attitude of the Ohio Experiment Station toward conclusions 

 drawn by the Bureau of Soils from work in cooperation with that station by 

 this method is defined in this circular. 



Suggestions regarding the examination of lands, E. W. Hilgard {Cali- 

 fornia .s7o. Circ. 2.T, ]ip. 7). — The purpose of this circular is stated to be "to 

 fornuilate some general explanations on the subject, which ma.V in many cases 

 enable the farmer to come to a definite forecast or conclusion, without indi- 

 vidual consultation and advice; or, when this is not attainable, may so instruct 



