Blimey there's lot's of poisonous plants, trees and funghi
Hemlock and hemlock water dropwort, as mentioned, different plants but both umbels, foxglove, Lily of the valley, lords and ladies (arum). Henbane and deadly nightshade contain hyoscine,scopoamine and others that attack the central nervous system, and cause delirium, convulsions and blurred vision and can lead to death, funnily enough deadly nightshade is a member of the potato family. Dog mercury, guelder rose, yew, all poisonous. Some are caustic like the spurges sap and giant hogweed and I can testify very well that arum leaves will burn your mouth. I once mistook a young arum leaf for common sorrel and took a luckily small taste, it really was caustic and burnt my mouth.
Fools parsley, another umbel that contains coniine (same as hemlock)
Death cap, panther cap, fly agaric, devil's boletes.....etc
Some plants poisons can be neutralised by heat (cooking).
It would be interesting to compile a list of the plants/trees/funghi to avoid, and maybe the nasty chemicals they contain and symptoms if ingested or touched. Might be an interesting thread.
About 4 years ago I remember reading somewhere some bloke committed suicide by eating foxglove leaves.
