Your Juanulloa mexicana is in the Solanaceae Family of plants. Being a tropical plant I doubt seeds require any stratification.
For most plants in the Solanaceae Family, plant the seeds fairly shallow and keep soil on the warm side. If the seeds are large and hard coat or have a corky coat, break the coat at least half way around the seed before planting. Keep the soil moist but more on the dry side of moist.
