I~I.-l~~l)i)ll~it~eI,fa,.?/ Note to (1 Memoir 0i1 the power ctscribcd to the Roots of Ph/s of q~’t(:hgpoisoriotis or (ib~iormabst& Ytuiices ymeiiteil to tAenz. By CHA~~LES DAUUESY,XU. F.R.S. M.R.S.B. Foreign Associate of tlic Koyal Academy of Munich and Professor of not ally Osfiml. IN a iiienioir rend heforc the Cliciiiical Society in May last and siiicc publishcd in the Society’s Journal,* I intiinatcd my intention of coiitiriuing the researches hcgun last year rc On tlic power ascribed to tlie roots of plants of rejecting poisonous or ahiormnl substances prcscnteil to tlictn ;”and as in the experiments thercin detailed tlic foreign iiigredients hail beeu applied to tlic plants after thy had sprung from the ground in the liquid form by watering them with the solution and it IVBS conceivable that some sniall portion might have adhcrcd to their external surfacc8 although none was actually absorbcd 1)y the roots,-I this year endeavoured to avoicl that sourcc of crror by introducing the salt into the soil before the secd \\a.’ 3 SOW11. The abnormal substanccs tried wre as bcfore the earths strontia and baryta ill combination with nitric acid,-aiid the metal nrseiik wliich however was applied not iii thc form of arsenious hut of arscnic acid which latter being isoinor-phous t;vith phosphoric acid might it mas coiiceived be substitutcd for it in tlic organism of a plant and thus bccornc assiimilatcd morc readily than arscnious acid. Thc crops tricd were as on the former occasion barley and tnr-nips aiid in neither of the two did any yery marked differcncc in the quantity of the crop olhined arise from the application of tlie salt.If ally thing the advantage seerncd to bc rather 011 the side of tliosc portions of tlic field which had been thus treated. Thc crops were scvcrally cxamined in the same manner as those of the year preceding had hen; but in no one of thc six caws three hcing the samples of tiirnips tried with arsenic baryta and strontia mid tlirce tliosc of barley treated with the same substances did any indications of the poisonous or abnormal ingredient which had been introduced into the soil manifest them- selves iii the resulting crop. * Vol. xiv 1’. 209. FOBTER ON PIPERIC AND HYDROPIYERIC ACIDS. I consider these results as rather more conclusive than those obtained in the preceding year because the substance experimented with being incorporated with the soil before the seed had been sown could hardly fail to get into contact with the roots at some part or other.The only question that can arise is whether the quantity ad- ministered was in each casc sufficient to become appreciable in the plants that had grown in contact with it. In the case of the arsenic I hardly know how this point could be determined more fully as a larger dose of the poison would be fatal to the vitality of the plant and thus the very conditions of the problem would be vitiated. With regard however to the strontia and baryta where this objection does not seem to exist it might be well to settle the point more conclusively by trying whether the earth would be taken up when quantities of either larger than were this year employed had been introduced into the soil.