I just want to share the experience I just had with the seeds of a citrus relative, Limonia acidissima:
I generally soak the seeds for 20 minutes in 4% H2O2 as this both cleans them and reduce the chances of the seeds rotting before they germinate, and might improve germination speed. This is not very important, but I did this for a batch of 20 seeds.
I then sowed 10 of them in sterilized dirt, and 10 of them on a moist paper towel (also somewhat sterilized by using boiling water). The dirt and the paper towel were both placed in small plastic pots with a lid next to each other. In the dirt, three seeds sprouted after two weeks or so while the seeds on the paper towel stayed inert for (checking my notes...) almost two months. They didn't rot because of how I treated them, but they didn't germinate either. I thought maybe I didn't wait long enough for the water to cool down and the seeds might have been cooked. But last week I transplanted the last seedlings from the dirt into individual pots, and I thought I'd put the paper towel seeds in the dirt to see what happens, and a few days ago I noticed that one of them sprouted.
So that's the first time I notice it, but something prevented these seeds from germinating on the paper towel. Maybe they are sensitive to light (citrus seeds aren't, as far as I know, and this is a close relative, so I'm rather surprised). Maybe this paper towel had some kind of inhibiting chemical but I've used the same roll to germinate dozens of other citrus seeds. So I'm not sure, but I found this experience interesting.