Hi Mary Sue, I think that there has been some confusion about this genus. In 1994, Heinrich & Goldblatt re-classified two Rigidella species into Tigridia in their Flora Mesoamericana. The two species were R. immaculata and R. orthantha. As far as I can see, they did not lump the whole of Rigidella into Tigridia. However, in 1996, Serna and Lopez-Ferrari re-established the genus with its four species (R. flammea, insusitata and the two above) as part of their contribution to the Flora of Mexico. That is the treatment that is accepted by Kew. As with many other "issues" in botany, you pay your money and make your choice. Both are equally valid. However, it does seem to me that using the latter means that it is part of a widely accepted, generally accessible model. Best regards, David Victor