In the First Part of this inquiry, the author gave an account, in 1840, of some observations made by him, as to the influence of season on the activity of the acrid plants of the natural family Ranunculaceœ, and of the narcotics belonging to the family Drupaceœ. In the Second Part now laid before the Society, he proceeded to relate a series of experiments instituted by him with the view of determining the influence of season on the activity of the poisonous narcotic plants of the family Umbelliferœ.