IV. THE EFFECT OF SALTS AND ACIDS ON BIOCOLLOIDS 

 AND CELL-MASSES. 



A proper supply of certain salts in the substratum is one of the most 

 important requirements of the plant, and those known to the physiolo- 

 gist as necessary for growth and development are designated as ''nutri- 

 ent salts," although more properly to be designated as culture salts. 



Available analyses show the general proportion of the various sub- 

 stances present in the organs and tissues of many kinds of plants. The 

 specialized or localized accumulations in the regions of the cell have 

 been demonstrated of only a very few substances, of which iron and 

 potassium seem to be the most notable.^ Chemical unions or precipi- 

 tations may account for the local concentration in some cases, while in 

 other structures the surface tensions of the minute masses of gels or 

 liquid may be responsible. 



The heterogeneous character of living matter and the known facts 

 of its hydration and that of biocolloids by which water, acids, and 

 salts, etc., enter into combination in both definite and indefinite pro- 

 portions with the colloidal material, together with the behavior of 

 cell-masses in imbibition, have made it seem inadvisable to attempt to 

 express the reactions obtained in terms of hydrogen-ion or hydroxyl- 

 ion concentrations, and but few measurements of this kind are cited in 

 the experiments described in the present paper. Although this method 

 entails a treatment empirical to a certain extent, yet forced parallel- 

 isms and false explanations resulting from the application of simple 

 formulae to complex phenomena are avoided. Attention has been 

 confined chiefly to the study of the action of solutions in which dis- 

 sociation may be assumed to be complete or nearly so. By following 

 this simplified procedure it has been possible to explore wide fields of 

 biological possibilities, the exact mapping of which will need con- 

 centrated attention upon comparatively narrow problems. This is 

 especially true of the action of the amino-compounds upon biocolloids, 

 concerning which certain preliminary results are described in the fol- 

 lowing pages. 



The amount of acid or salts and of water which may be taken up 

 from a solution and the accompanying swelling is influenced by several 

 factors. The reader is referred to texts on physics and on colloids for 

 detailed discussions of adsorption equations and for information con- 

 cerning the allowable generalizations concerning the relative amounts 

 of material which may be taken up by a colloid from a solution system. 



For the present some results recently obtained by Miss C. L. Carey 

 and as yet unpublished will be of interest, as the absorption of water 



1 MacCallum, A. M. The distribution of potassium in animal and vegetable cells. Jour, of 

 Physiol., 32 : 95. 1905. Also, Presidential address, Brit. Assoc. Adv. Sc, Report for 1910, p. 744. 



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