The presence of manganese as a constituent of plant tissues has been known for many years, and in view of the close association between iron and manganese it was natural that the early investigators should seek for the latter element. De Saussure (1804) gives one of the earliest references to manganese in plant ash, stating that it occurs in the seeds in less great proportion than in the stems, and also that the leaves of trees contain less in autumn than in spring. At first oxides of iron and manganese were put together as “metallic oxides” and little or no attempt was made to separate them so as to get an idea of their relative abundance. John (1814) gives a number of rough analyses of plants and indicates the presence of manganese in many plants, including _Solanum tuberosum_, _Brassica oleracea viridis_ L., _Conium maculatum_, _Aesculus_ (in outer bark), and _Arundo Sacchar_. No further references presented themselves until 1847, as probably manganese was overlooked and always classed with iron in any analyses made during that time. Kane (1847) found traces of manganese in the ashes of some samples of flax, but none in others, and examinations of the soils on which the plants were grown gave similar results. Mayer and Brazier (1849) confirmed this result. Herapath (1849) analysed the ashes of various culinary vegetables, finding manganese in cauliflowers, swede turnips, beetroot, and in one variety of potato (Forty fold). Malaguti and Durocher (1858) tried to investigate the matter quantitatively. The oxides of iron, manganese, and aluminium were all classed together, and the mean percentage of the three varied from ·85%–5·06% according to the varieties of plants concerned, Cruciferae possessing least and Leguminosae most. Different mean results with the same plant were obtained from different soils. Wolff (1871) made other quantitative analyses including _Trapa natans_ (·15% Mn₃O₄), _Acorus Calamus_ (1·52% Mn₃O₄), _Alnus incana_ (trace–·73% Mn₃O₄), _Pyrus communis_ (2·15% Mn₃O₄). Many other plants were mentioned by Wolff as containing manganese. Campani (1876) found manganese in ash by a method in which it was detected as phosphate of manganese, and he claimed to be the first to discover manganese in wheat ash. Warden (1878) found traces of Mn₃O₄ in the ash of opium from Behar. Dunnington (1878) detected manganese in the ash of wheat, ·00144 gm. (as Mn₃O₄?) in 300 grams of “Dark Lancaster” variety, equivalent to ·027% of the pure ash. The ash was exhausted with nitric acid, and after separating the iron the ammonium sulphide precipitate was found to contain manganese, and gave by fusion with nitre and sodium phosphate a violet coloured mass. Andreasch (1878) found slight traces of Mn₃O₄ in the flowers of _Dianthus caryophyllus_, none occurring elsewhere, while in _Rosa remontana_ it appeared in both leaves and flowers.