AGRICULTURAL BOTANY. 729 



The solvent action of roots, F. V. Chirikov (Zhur. Opytn. Agron. (Rtiss. 

 Jour. Expt. Landic), 15 {19W, No. 1, pp. 54-65). — As the result of experiments 

 carried out with barley and buckwheat in nutritive media, the author con- 

 cludes that the excretion of acids by roots is inadequate to explain a num- 

 ber of facts noted in connection with the nutrition of the higher green plants. 

 Roots of such plants are surrounded by a solution which is in a certain state 

 of equilibrium. Roots of different plants disturb the equilibrium in the medium 

 in very unlike ways, absorbing predominately calcium oxid or phosphorous 

 pentoxid, as the case may be, and the relations of these plants to phosphorus 

 pentoxid must differ considerably. Barley does not take up phosphorus pen- 

 toxid in the presence of calcium nitrate or other calcium salt, but it may utilize 

 phosphoric acid from phosphorite alone in considerable degree. Buckwheat 

 behaves differently, taking up phosphorus pentoxid from phosphorite in either 

 the presence or absence of calcium nitrate. This difference is explained on 

 the supposition that buckwheat takes up. from the nutritive solution, calcium 

 oxid more energetically than phosphorus pentoxid. while in case of barley, 

 phosphorus pentoxid is much more energetically taken up than is calcium oxid. 



Some factors which influence the water requirements of plants, P. Khan- 

 KHOJE {Jour. Amer. Soc. Agron., 6 (19U), No. 1, pp. 1-23, fig. 1). — These ex- 

 periments were carried out in order to ascertain more in detail some of the 

 factors influencing the water requirements of cereals, standard methods being 

 employed. 



It is stated that different kinds of crops require dift'erent amounts of water 

 to produce a unit of dry matter. Increased strength of soil solution decreases 

 water requirement. A fertile soil with limited water supply will produce a 

 larger crop than will an infertile soil under similar conditions. Young plants 

 require moi-e water than older plants. Plants furnished with excessive water 

 come to require more wnter per unit of dry matter than do plants grown in 

 drier soils. 



The relation of atmospheric evaporating power to soil moisture content at 

 permanent wilting- in plants, J. W. Shive and B. E. Livingston (Plant World, 

 17 (1914), No. Jf, pp. 81-121, figs. 5). — The authors, giving a detailed account of 

 their investigations, state that these have substantiated the claim of Caldwell 

 (E. S. R., 29, p. 523) to the effect that the amount of water left in any given 

 soil at the time of permanent wilting of plants is a function of the intensity of 

 atmospheric evaporating power for the period during which permanent wilting 

 is attained. They further hold that the conclusion reached by Briggs and 

 Shantz (E. S. R., 26, p. 628; 27, p. 223), to the effect that the atmospheric and 

 environmental conditions that obtain during the process of wilting have little or 

 no effect upon the residual water content here considered, and that this soil 

 moisture residue for any given soil remains constant for all species of plants 

 grown in it and for various stages of development, can not be considered as of 

 general application but only as expressing a relation obtaining under some as 

 yet undetermined range of external and internal conditions within which must 

 have lain the experimental conditions employed by these workers. 



Acidity of manures as related to germinability of seeds of leguminous 

 weeds, O. Munerati and T. V. Zapparoli (Staz. y^per. Agr. Itah, 46 (191.3), No. 

 1, pp. 5-17). — Field and laboratory tests were made with seeds of Vicia segetalis, 

 v. hirta, and Lathyrus aphaca from 2 to 6 years old in contact for different 

 periods with acid phosphate of varying strength. It was found that long con- 

 tact and strong solutions both corresponded with the progressive diminution 

 of germinability of the seeds. This result is thought to be related to an increase 

 in permeability of the seed coats. 



