Optional: Throw out another land, then tap it to activate the Mantle, give the Dryad +2/+2 and untap it at the same time...
...tap the Dryad for a green mana and one of any color; activate the Mantle; untap the Dryad...
...tap the Dryad; activate the Mantle, untap the Dryad...
...tap; activate; untap...
...
,
+2/+2,
...
...et cetera...
...etc...
...