S. H. Collins (1902) found that barley is able to absorb relatively large quantities of arsenic. The plants were grown in pots on soil which originally contained a certain amount of the substance, and various combinations of arsenic acid, arsenious acid and superphosphate were added. Particulars and details are not given by the author, except that arsenic was detected by Reinsch’s test in the grains from all the experimental pots, and in one case (not specified) in the upper and lower halves of the straw and in the threshed ears. The analyses of the soil at the close of the experiments showed the presence of 7–22 parts arsenious acid per million. Wehmer (1911) quotes references to the occurrence of arsenic in _Vitis vinifera_. The element was detected in the ash of the must and its presence was attributed to treatment of the plants with arsenical compounds. In this connection it is interesting to note the observation of Swain and Harkins (1908), who, while acknowledging the absorption of arsenic from the soil by many plants, yet indicate that in the case of those plants which are exposed to smelter smoke the arsenic is deposited on the vegetation, and is not absorbed by the latter from the soil. II. EFFECT OF ARSENIC ON THE GROWTH OF HIGHER PLANTS. 1. _Toxic effect._ (_a_) _Toxic action of arsenic compounds in water cultures in the presence of nutrients._ The poisonous action of arsenic on plants has long been recognised. Chatin (1845) gave accounts of tissues poisoned by strong arsenical solutions. Nobbe, Baessler and Will (1884) carried on water culture experiments with buckwheat, oats, maize and alder, and found that arsenic was a particularly strong poison for these plants. When small quantities of arsenious acid (As₂O₃) were added to the food solutions, growth was measurably hindered by a concentration of 1/1,000,000 As (reckoned as As). The element only appears in plants in very small quantity and can never be detected in notable quantities. The aerial organs show the effect of arsenical poisoning by intense withering, interrupted by periods of recovery, but eventually followed by death. It was also found that if plant roots were exposed to the action of arsenical solutions for a short period, say ten minutes, and then were transferred to normal food solutions, the action of the poison was delayed, but eventually hindering of growth or death occurred, according to the strength of the poison used in the first solution.