Point To Point Bridge Question

[itd17]

I've never quite understood this one:

Say I have a point-to-point configuration

router--root bridge (wireless link) non-root bridge--clients

How does the frame passed from a client on the non-root side know how to use the wireless link to get to the gateway? It will carry the mac of the ethernet side of the gateway, so just don't understand how the bridge will pick up the frame and pass it over the wireless link.

Thanks for any information.