Macroscopic learners need to see the whole X-Mas tree before they start to hang the ornaments.

FORBES: Totally Addictive Education: The Future of Learning

The subspecies of cicadas known as Brood X has been underground for the last 17 years, tapped into tree roots, feeding and fattening up.

NPR: Roar of the Cicada

"X Marks the Spot" is a song on Sample's 2002 Album, "The Pecan Tree, " dedicated to his Houston roots.

NPR: A Jazz Single Sees One Man Through