What is The Poison?

Socrates' execution comes about as the result of his taking poison - according to legend, that derived from the hemlock plant. It's interesting to note that the moment of death is the direct result of Socrates' own action. He's not hung or shot or beheaded, he's not injected with the poison - in other words, his death is not actually done to him, but he does it himself. There is perhaps a deliberate irony in this - it's possible that where those who tried and condemned him saw him as creating his own fate by saying what he did, they see justice in him being literally the means to his own end. Yes, they give him the poison, but he takes it himself.