What does the March Hare wear on his head in Alice's Adventures in Wonderland?

Tenniel's original illustrations for Alice's Adventures in Wonderland depict the March Hare as wearing straw on his head. During the Victorian age, this was a convention used to indicate madness or insanity.

From Lewis Carroll's Nursery "Alice":

That's the March Hare, with the long ears, and straws mixed up with his hair. The straws showed he was mad-I don't know why. Never twist up straws among your hair, for fear people should think you're mad !

To see Tenniel's illustrations of the March Hare, follow the related links below.