Phil, the sub-genus Diaphoranthema consists of the smallest tillandsias, many with inconspicuous, tiny brown/yellow flowers. Crossing these species with one another or other species is tough due to the tiny sexual parts of the flowers. Recurvata and usneoides have been crossed with each other to make "Kimberley" and usne. x mallemontii to creat "Nezley". I'm not aware of any other crosses although there may be natural hybrids among species of each group out there somewhere waiting for discovery.

thanks gonza