Tkinter add_cascade option_add

[Bob Greschke]

Root.option_add("*?????*font", "Helvetica 12 bold")

Want to get rid of the "font =":
Widget.add_cascade(label = "File", menu = Fi, font = "Helvetica 12 bold")

Does anyone know what ????? should be to control the font of the cascade 
menus (the labels on the menu bar)?  "*Menu*font" handles the part that 
drops down, but I can't come up with the menu bar labels part.

Thanks!

Bob