Sea Fern

Things that really exist that could go in the Avatar movie.
No. 1: The Sea Fern.
Transported into the Alien Forest Jake Sully approaches what looks like a fern with tiny berries on it. Looking closely he sees that inside each berry is a jellyfish, he touches one and it stings him, pulling his arm back in shock he knocks another fern and dozens of tiny jellyfish swim into the air around him.
Guardian: Nicolas Voutnis