I have come across an issue recently whereby certain webcams are not enumerated correctly in a Xendesktop session. The issue appears to be with certain webcams and there lack of support for switching to the default resolution of 352 x 288.
By modifying a certain key within the registry you can fixed the setting to a more common resolution ie 320 x 240.
The registry key in question is the HKEY_CURRENT_USERSoftwareCitrixHDXRealTime you will need to create the following values:-
Data: 320 (decimal)
Data: 240 (decimal)
Once this is added you should see that the webcam gets redirected within the session without any problems.