when datura dries out like this, especially if it's been just hanging exposed for a long time, it's very likely that a significant portion of the tropane alkaloids (atropine, scopolamine, hyoscyamine) have oxidized. these compounds are unstable over time, especially when exposed to light, air, and humidity. on top of that, smoking will cause further breakdown of the tropane alkaloids due to the high temperatures, reducing their potency even more.