| Abstract: | Analyses have been made of the inorganic constituents of the juices expressed from the leaves of Rheum, Rumex, and Oxalis. It has been shown that in all cases there is a large excess of inorganic cations over anions in the sap, the average ratio of cations to anions being 3.8 (Part 1, p. 239). The ash analyses of plant tissues (chiefly leaves) reported in the literature have been examined critically, and it has been shown that the preponderance of inorganic cations over inorganic anions in the ash and in the sap is general. It has been concluded that the excess of inorganic cations is consistent with the view that cations pass into the protoplasm chiefly in the form of hydroxides, and are accumulated either in the form of organic salts (such as the oxalates) or in non-polar linkage. It has been concluded that practically all the potassium and sodium found in plant ash must have been present originally in the form of soluble ionogenic compounds, but that a considerable part of the calcium and magnesium may have been present originally in the form of insoluble salts or as components of non-polar compounds. The methods whereby the cations, particularly potassium, may have been accumulated have been discussed, and it has been concluded that as it does not seem very probable that they enter chiefly as nitrates or bicarbonates we may suppose that they go in to a large extent as hydrates: this is highly probable in the case which has been most carefully investigated (Valonia). |
