Woodchip Sliver

As Woodchip Sliver enters the battlefield,
sacrifice any number of untapped Forests or
untapped Slivers.
All Slivers have base power and toughness equal
to the total number of Forests and Slivers
sacrificed as Woodchip Sliver entered the battlefield.
Guy: That's a sliver?... I don't even see it...
Zeekus: Trust me, it's in there!