It doesn't matter.
The paper towel is so you can see that your stuff did actually germinate whereas, in soil, thats hard to verify (pythium is common destroyer of seed that just popped open).
I just put them in water at room temperature to reduce the amount of blank cells when doing seed tests.
Originally Posted by plantingplants
So I had 20 seeds. I put 10 in wet paper towels, and 10 in moist soil on a heat mat. I planted the 10 when they cracked. The paper towel seeds broke ground first by two days.
These results aren't conclusive because of two variables I couldn't accurately measure or control in the soil. Moisture level and temperature. The wet paper towels were more moist and warmer. I believe if those two variables are identical, media doesn't matter as long as the seeds are in direct contact with it.
Further experiments to come.