Either put a stop() in frame 20 of the main timeline or extend the tree for the length of its animation on the main timeline if you have more to add to the main timeline after it.
What is happening is you are going back to frame 1 when you reach frame 20 so the tree never has a chance to play thru.
If you need to learn how to working with masking, then search Google for a tutorial using terms like "Flash animated mask tutorial" - that will provide plenty of results
If you already know how to work with masking, then you either need to just start working on it or you need to explain what your problem is.
murphy my problem is not a masking.
I want to play my movie clip run one by one
1) I am created a stem movie clip
2) Created leaf movie clip
3) Swiral movie clip all movie clip i am incorporated a stop() action because not repeat
When my stem masking complted, i want to play next my leaf movie clip, then swirel movie clip
how can i do this?
Just build you animjations along the main timeline instead of in movieclips. That way you can place them one after another.