Taxonomic Notes on Houstonia purpurea var. montana (Rubiaceae)

Houstonia purpurea var. montana is restricted to the summits of Roan Mountain, North Carolina-Tennessee, and Grandfather Mountain, North Carolina. Morphological and cytogenetic data support varietal rank for it instead of specific rank as H. montana. Correct authorships for these names are discussed. A recent finding of sterility in crosses between H. purpurea var. purpurea and var. montana could have been caused by ploidy differences alone rather than by more fundamental differences. Houstonia purpurea var. montana is subjected to increasing human encroachment and should be considered as threatened or endangered.