Hi Alan,
Most any Ipomoea species responds well to being nicked or lightly abraded and then soaked overnight in warm/hot water before sowing. You can skip the abrading step and just soak overnight to hasten germination for most species. Either way, the seed coat will swell and start breaking apart, often while still in the water.
I soak Thunbergia alata 24-36 hours in warm water, too. Germination usually takes about a week.
