"The flowers appeared along the midvein of the 'leaf'"

the proper term is rhachis. The. Megaclinium Group of Bulbos all have a flowers along a rhachis. They are all from the African continent. Purpureorhachis is the most robust of this group. I purchased a division of this species last year. The species name means: purple-red colored rhachis. Other members of this group include falcatum, maximum, sandersonii and many others.