SOIL, climate, time of sampling and other factors influence the mineral composition of plants, and the same species can contain a wide range of inorganic ions. In spite of these variations several workers1–3, using different plants, claimed that the sum of the cations (expressed in m.equiv./100 g dry material) of a particular plant is constant. McCalla and Woodford4 found that the ratio of total cations : total anions in wheat was constant and later Bear5 showed that, for lucerne, at any pH when ions were expressed in m.equiv./100 g: It is not known if silicon should be included, and Dijkshoorn6, using perennial ryegrass, obtained a constant = 0.5 when silicon was omitted.