The presence of zinc in the ash of certain plants has been recognised for many years, especially in so far as the vegetation of soils containing much zinc is concerned. Risse, before 1865, stated that most plants when grown on such soils prove to contain greater or less quantities of zinc oxide. He states that the soil at Altenberg, near Aachen, is very rich in zinc, which rises as high as 20% in places. The flora of the soil is very diversified and zinc has been determined qualitatively in most and quantitatively in some of the plants. _Viola tricolor_ and _Thlaspi alpestre_ are most characteristic under such circumstances, both showing such constant habit changes that they resemble new species, while other plants such as _Armeria vulgaris_ and _Silene inflata_ are peculiarly luxuriant. Risse’s figures of the zinc content of these four plants may prove of interest. The figures are based on the dry weights, air dried. _Thlaspi alpestre_, var. _calaminaria_. Root 6·28% ash, 0·167% ZnO, 1·66% ZnO in ash. Stem 11·75% „ 0·385% „ 3·28% „ „ Leaves 11·45% „ 1·50% „ 13·12% „ „ Flowers 8·49% „ 0·275% „ 3·24% „ „ _Viola tricolor._ Root 5·59% ash, 0·085% ZnO, 1·52% ZnO in ash. Stem 10·55% „ 0·065% „ 0·62% „ „ Leaves 9·42% „ 0·110% „ 1·16% „ „ Flowers 7·66% „ 0·075% „ 0·98% „ „ _Armeria vulgaris._ Root 4·74% ash, 0·17% ZnO, 3·58% ZnO in ash. Stem 5·37% „ 0·02% „ 0·37% „ „ Leaves 9·36% „ 0·11% „ 1·17% „ „ Flowers 6·08% „ 0·07% „ 1·15% „ „ _Silene inflata._ Root 2·71% ash, 0·02% ZnO, 0·74% ZnO in ash. Stem } Leaves } 11·43% „ 0·22% „ 1·92% „ „ Flowers } Freytag (1868) carried out various experiments on the influence of zinc oxide and its compounds on vegetation, and found that all plants are capable of absorbing zinc oxide by their roots when grown on soils containing such oxide. Generally speaking the zinc is deposited chiefly in the leaves and stems, very little being found in the seeds, such minute traces occurring that he stated that the seeds must be harmless for men and animals. The general content of ZnO in plants is given as ·5–1·0% of ash, except in the abnormal case of plants growing on calamine. Lechartier and Bellamy (1877) demonstrated the presence of zinc in such food substances as wheat, American maize, barley and white haricots, but they failed to find it in maize stems and beetroot, so they cautiously concluded that if it does occur in the latter cases it must be far less in quantity than in the former. Hattensaur (1891) analysed the ash of _Molinia cærulea_ and discovered the presence of copper, manganese, zinc and lead, zinc oxide forming ·265% of the total ash, (·006% of the air dried plant).