1994 Ford Escort Transmission leak

Hi,
On my Escort wagon, I recently had my rear pump seal fixed as it was leaking. Now the issue I'm having is that there is a small black rubber hose with a brass plug in it, located towards the front of the cars underside, and this is leaking transmissino fluid. Fluid is coming from the end of this rubber hose, even though there is a plug in it. So I have a two part question. What is this rubber hose piece, and why would it be leaking transmission fluid. How can I stop it leaking? The brass plug is not hollow, but a solid piece. Any help would be appreciated.