While Jensen denied stimulation in wheat grown in water cultures even when the solutions were as dilute as _n_/100,000 zinc sulphate, yet he found increase of growth with the same plant in artificial soil (quartz flour) to which much stronger solutions of zinc sulphate, from 5_n_/10,000–_n_/10,000, had been added. (_c_) _Increased growth in soil._ Nakamura (1904) dealt with a few plants of agricultural importance, adding ·01 gram anhydrous zinc sulphate to 2300 grams air-dried soil. The marked individuality in the response of the various plants to the poison is very striking. Allium showed signs of increased growth throughout; Pisum was apparently improved in the early stages of growth, but when the dry weights were taken at the end of the experiment no increase manifested itself in the weights of the plants treated with zinc; with Hordeum the same quantity of zinc exercised a consistently injurious action. These results with peas and barley corroborate those obtained in the Rothamsted experiments with water cultures in that zinc sulphate proved to be less toxic to peas than to barley. Kanda found that both peas and beans when grown in soil as pot cultures were improved by larger quantities of zinc sulphate than when they were treated as water cultures--a result in full accordance with current knowledge. Wheat is evidently peculiarly sensitive to the effects of zinc compounds under differing conditions. Javillier (1908 c) pointed out that while wheat is very susceptible to the toxic action of zinc, yet it can benefit by the presence of sufficiently small quantities of the compounds of the metal. Rice is another cereal that is said to respond to the action of zinc sulphate, as Roxas, working in pot cultures with soil both with and without the addition of nutritive salts, obtained an acceleration of growth on the addition of _m_/1000 zinc sulphate, a quantity so remarkably great that it might be expected to act as a toxic rather than as a stimulant. With phanerogams the zinc question is not only concerned with the effect of the metal upon germination, but also with its effect upon the later growth of the green plants, and on the physiological functions involving the construction of substances at the expense of mineral elements and the carbon dioxide of the air. Javillier holds that the indications are that zinc would prove to be profitable if applied to crops as a “complementary” manure. 4. _Direct action of zinc salts on leaves._ Dandeno (1900) applied zinc sulphate in drops to the leaves of Ampelopsis, and found that the solution was not all absorbed by the leaf, but that a slight dark ring of a yellow colour was produced, and he was induced to think that some local stimulation was produced if the salt was presented in sufficient dilution.