My exhaust is glowing on my lawn tractor

I have a MTD yardman riding mower and I noticed that the muffler was glowing red hot, and there were flames coming out of the exhaust. I am not really sure how to fix this or really where to start. I would like to fix this on my own if I can, rather than hiring someone to fix it.
Here are links to a video and a picture of the exhaust glowing:

http://ift.tt/1KJ2Fsp

http://ift.tt/1KJ2FIJ


Thanks,
Logan

My exhaust is glowing on my lawn tractor