Interesting results were obtained (Agulhon 1910 a) by repeated experiments with the same soil containing boron. It was found that sand or soil containing a proportion of boron which is lethal or toxic to a first culture will allow much better growth with a second and subsequent crops. Repeated experiments on the same soil may show the change from a lethal dose to a toxic one, thence to an indifferent and finally to an optimum concentration. Furthermore (Agulhon 1910 b) the very plants may accustom themselves to greater quantities of boron, the increased power of resistance being transmitted. He concluded from his experiments that the progeny of the second generation of maize were able to withstand quantities of boron that were toxic to control plants[13]. Agulhon once again emphasised the fact that for toxic doses of boron the first symptom is the more or less marked disappearance of chlorophyll, though the aerial parts are not affected so soon as the roots. [13] “Il apparaît donc que les graines fournies par des plantes ayant crû en présence d’une quantité de bore élevée présentent une accoutumance vis-à-vis de cet élément; les plants auxquels elles donnent naissance semblent non seulement faire un meilleur emploi des petites doses de bore qui leur sont offertes, mais encore supportent les doses toxiques plus facilement que les plants témoins, issus de graines non accoutumées.” 2. _Effect of boron compounds on germination._ One of the first indications that boron compounds affect the germination of seeds was given by Heckel (1875) who found that germination was retarded for 1–3 days by weak solutions of borates (·25 gm. to 20 gm. water), and was stopped altogether by stronger solutions (·60 gm. to 20 gm. water). Archangeli (1885) tested the germination of a variety of seeds of Leguminosae, Gramineae, and of Cannabis, Iberis, Raphanus, Collinsia, and Linum in the presence of boric acid. The seeds were placed in bowls with solutions of ·25, ·5, and 1% boric acid at temperatures ranging from 16°–23° C. The bowls were covered with glass plates to prevent evaporation and consequent increase of concentration, controls in spring water being dealt with under similar conditions. 1% boric acid was found to check germination altogether, and the weaker the concentration the less was the process hindered. Morel soaked seeds of haricots and wheat in various solutions of boric acid, and found that germination was generally hindered or inhibited. The deleterious action diminishes as the strength of the solution or the time of contact diminishes, but solutions of the same concentration do not act equally on all seeds. Boric acid and borax proved to be similar in their action qualitatively. The deleterious effect of strong doses of boric acid on germination was confirmed by Agulhon (1910 a), the higher quantities (above 10 mg. boric acid per litre) retarding germination of wheat. 3. _Does boron stimulate higher plants?_