Double embryo seeds?

I've just germinated some Salvias from seed I'd saved off my own plant. I got a high germination rate and every single one has come up apparently with two plants out of each seed. What's going on?

 

I've grown a large number of Salvia species from seed and to the best of my knowledge they are not polyembryonic. Certainly never seen it happen myself.
Which species are your seed from?

 

.....um, I was being thick. When the second lot germinated from my other plant I realised what was going on. They are single embryos with no hypocotyl emerging from the seed, it's just the petiole bits of the cotyledons coming out of the seed the popping up 3cm above the compost.