The List

Sprout Swarm

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Create a 1/1 green Saproling creature token.

Future Sight

Convoke (Each creature you tap while playing this spell reduces its total cost by {1} or by one mana of that creature's color.)
Buyback {3} (You may pay an additional {3} as you play this spell. If you do, put this card into your hand as it resolves.)
Put a 1/1 green Saproling creature token into play.