gotoAndPlay from different Movieclip

Hi,
Pretty straight forward question I think!

I have a movieclip on the stage instance name: “man_mc”
and another movieclip on the stage named: “tree_mc”

At the end of the timeline in “man_mc” I want to call the “tree_mc” to gotoAndPlay(‘fall’).

I’ve tried tree_mc.gotoAndPlay(‘fall’); and a few others, but I’m having no luck!

Any help would be much appreciated!