Creature — Elf Druid 1/1, G (1)
Uncommon
Tap three untapped Elves you control: Add {G}{G}{G} to your mana pool.
"Study the great spirits of our age and those of the past. Prune secrets from the branching traceries of our lineage."
—Twila, Gilt-Leaf archdruid
Illus. Larry MacDougall

4/1/2008: Since the activated ability doesn't have a tap symbol in its cost, you can tap creatures (including Heritage Druid itself) that haven't been under your control since your most recent turn began to pay the cost.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern