MGB: 79 cannister hose?

79 midget question. I get better replies over here.....
Can someone tell me if the middle hose coming off the top of the cannister by the firewall is attached to anything? It runs by the coolent reservior and ends to nothing on my car. Might be that it's designed as a vent?

Thanks!!!

See this from the site's library:
http://www.mgexperience.net/article/weber-hose.html