Long before any experimental work was done with boron in water cultures, the poisonous properties of the substance were recognised with regard to plants growing in soil. Peligot (1876) grew haricots in porous earthenware pots, the plants being watered by rain and by solutions, each containing about 2 grams per litre of such substances as borax, borate of potassium, and boric acid, other pots receiving various fertilisers, as potassium nitrate, sodium nitrate, &c. This quantity of boron completely killed off the plants receiving it, whether it was applied as free or combined boric acid, while the fertilised plants completed their development well. On this account the deleterious action was attributed to the boric acid and not to the sodium or potassium base supplied. Peligot hinted at the improbability of a substance like boron, which is so poisonous to plants, being really innocuous to human beings when it is used as a preservative for foods. Nakamura (1903) also found that borax is harmful in pot cultures if present in large quantities, 50 mg. borax per kgm. of soil exerting a very injurious influence, while even 10 mg. per kgm. did some damage. Agulhon (1910 c) found that the toxic doses of boric acid in soil cultures approached those in nutritive solutions rather than in sand cultures, a phenomenon that he attributed to the fact that the boric acid was fixed by the soil, probably as insoluble borate of calcium, so that the surface concentration obtained with sand cultures was avoided. He found that the ash of plants grown with excess of boron contained more than the normal amount of boron, while the weight of ash per 100 dry matter was also increased. He concluded that the plant thus suffers an over-mineralisation and in consequence an augmentation of its hold on water, so that the fresh weight of the plant may indicate a more favourable action of the boric acid than does the dry weight. Other investigators (Fliche and Grandeau 1874) had found the same increase in the proportion of ash in chestnut trees grown on too calcareous soil, so Agulhon concluded that one is here dealing with a general reaction of plants to an excess of a useful element. Other experiments were carried on in the open field, maize being grown on control plots and on plots receiving 2 gm. boron per square metre. At first the latter plants were behind, the dose being too strong. Eventually, however, they pulled up level and the dry weights from the two plots proved to be nearly the same, the fresh weights being identical. Maize is evidently far less sensitive to boron poisoning than are peas and oats, for with these one-half the original amount of boron (= 1 gm. per sq. metre) proved toxic.