5 year old seeds may not sprout, how were they stored? Heat and/or temp fluctuations and high humidity detrimental to seed survival.

I put them in dirt, and they rotted. What I've since realizedis that they don't appear to actually be putting out a root. Its like the whole embryo is extruding out of the seed....

Sorry, no help here, pix might help with bolded area,

I have never had a whole lot of luck with the baggie and wet paper towel method. I have much better germination success with some commercial potting mix and a small starter cup. Even if you get them to germinate, then you have to extrude them from the paper towel and carefully put the little fellas into some soil. Seems this is another failure point in my experience.

I find it best to play the mother nature game and do it her way.

Thanks... if another one does the extruded goo thing, I'll take pictures. I did try both seed types in potting mix, under a dome, on a heat mat, and after 3 weeks I gave up.

So I guess seed swelling is not any kind of indication of viability - is that true?

3 weeks, that's a short time for old seeds to get going. I had wild pepper seeds that took 30 days to 60 days to germinate and I would treat old seeds the same. I've tried the paper towel method and years back swore by it. Now it's just too much of a hassle and extra step in the process that I no longer use it but if frustrated by non-sprouting seeds I may try that as one of the several methods I would try. As for what you are describing I would assume damping off fungus contaminated the paper towel or baggies. Did you work with soil planting some seeds and then work with the paper towel method? Other than that I'm not sure of what the cause would be.

I find that hot peppers take longer to sprout (I use the same paper towel/baggie method). Also, seeds may appear to sprout but if they are really old, they may not have the necessary reserves to grow into a plant.