"The story of Opium Jones" joke

First day of class in a rural Southern school. Teacher is calling role: "Billy Adams."
"Here."
"Susie Brown."
"Here."
She comes to "Opium Jones" and gasps. "Boy," she says, "what you name?"
"Opium Jones!" he says proudly.
"Boy," she says, "you go fetch yo' mammy to come see me."
The mother arrives.
"This boy say his name is Opium Jones," the teacher says.
"That's right," the mother says. "That's what we named him."
"But don't you know opium is a dope?" the teacher says.
"I sure do," the mother replies.
"No no no, that's not what I meant," the teacher says. "I mean, opium is illegal."
"Uh-huh," the mother says.
"No no," the teacher says. "What I mean is, opium is a seed what come from a white poppy."
"You hit the nail right on the head!" says the mother.