Hope this might be helpful to someone.

A. colubrina germinates quickly, but is prone to rot. The brown, papery seed coat retains moisture well, and can easily lead to the cotyledons rotting. I found the following approach, which is much more hands-on than I would normally use, to work best:

- soak the seed in room temperature water for an hour
- place the seed on top of moist seed starting mix in a humidity chamber. I use equal parts vermicompost, sand, and pumice in a pot sealed in a freezer bag. If your space is cold, use a heat mat underneath.
- as soon as the radical emerges, remove the humidity chamber. If the radical doesn't bury itself in the soil immediately, turn the seed over and guide it into the dirt. Keep the soil moist and the seed coat dry, if possible.
- as soon as the seed coat begins to split, manually remove it: put water on the seed coat and let it soften for a few minutes, and then gently cut/pull it off with tweezers and a scalpel, being careful not to nick or damage the cotyledons. If the cotyledons don't open within a few days, gently pry them apart.

With this method a germination and survival rate of 75% or higher should be possible. I suspect this level of care is necessary because the seeds aren't as fresh as in the wild, and the specific environmental needs of the plant are tricky to meet in captivity.

I'm attaching a picture of a young seedling where I used this method, and a rotten one where I didn't