The Collaborative International Dictionary of English v.0.48:

Houstonia \Hous*to"ni*a\, n. [NL. So named after Dr. William
   Houston, an English surgeon and botanist.] (Bot.)
   A genus of small rubiaceous herbs, having tetramerous
   salveform blue or white flower. There are about twenty
   species, natives of North America. Also, a plant of this
   genus.
   [Webster 1913 Suppl.]

U.S. Gazetteer Places (2000):

Houstonia, MO -- U.S. city in Missouri
   Population (2000):    275
   Housing Units (2000): 105
   Land area (2000):     0.197025 sq. miles (0.510292 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.197025 sq. miles (0.510292 sq. km)
   FIPS code:            33256
   Located within:       Missouri (MO), FIPS 29
   Location:             38.898487 N, 93.358869 W
   ZIP Codes (1990):     65333
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Houstonia, MO
    Houstonia