"Where's Hermione gone?" whispered Harry, "in fact, why aren't any of
the girls here?"

"I think they've gone off to have The Talk," Ron replied, earning a
glare from Professor Snape.

"What talk?"

Ron looked uncomfortable.  "About growing up, mainly."

"But why did they go off without us, then?"

"Mr Potter", interupted Snape, "you are supposed to be learning about
aconite, not gossipping."

The two friends worked in silence for a while, then Ron whispered
back, "Well, it's different for girls." 

A look of incomprehension drifted over Harry's face.

"Harry, you do know where little wizards come from, don't you?"