One of the other seed bracts on the sand palm has thrown the seeds off. I think maybe the ones I planted earlier were not yet ripe, they were much smaller and browner than these. I've collected 15 of them and put them pointy side up in a pot. I've got some cinnamon on the surface and I'm only watering them with a spray so as not to get the bottom of the soil wet and rotten. It was the only pot I had large enough for all the seeds but I think it is a bit deep.
I've got the pot in a sheltered terrace with only overhead light that is covered by mosquito screen. It gets an hour or two of direct sun a day at this time of the year.