I accidentally opened the pump head cap and the parts came out. Oops! It seems I can't remember which part that should go in the pump first...and which side?

I have a black rubber thing, white plastic ring, some weird white tube, and cap.

You can find the picture of my parts at: http://img580.imageshack.us/img580/6250/photoydy.jpg

I will appreciate it if you can help me! Thank you!