A NUMBER of independent investigators have examined the distribution of alkaloids in the tissues of Atropa1,2,3 and Datura1,2,4,5 seeds. They have used a variety of precipitants ; but principally iodine in potassium iodide, which, with the technique developed by Errera6 and his school, is the most dependable for revealing the whereabouts of alkaloids by precipitation within tissues. These workers are agreed that the belladonna and thorn-apple alkaloids are restricted in the ripe seed to the peripheral layers, that is, to the testa itself and especially to a thin layer of cells lying between the testa and the endosperm ; probably a perisperm derived from the nucellus. This curious distribution is also found in the seeds of Hyoscyamus1,4. It has been confirmed in my own laboratory for those of belladonna3. Barth5, examining Datura stramonium seeds that were not quite ripe, thought that there might be a little alkaloid also in the embryo and endosperm. Other investigators examining seeds that were fully ripe found none in either of these parts.