Houstonia (plant)

Houstonia (bluet) is a genus of plants in the family Rubiaceae. Many species were formerly classified, along with other genera since segregated elsewhere, in a more inclusive genus Hedyotis.

Houstonia
Houstonia caerulea
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Gentianales
Family: Rubiaceae
Subfamily: Rubioideae
Tribe: Spermacoceae
Genus: Houstonia
L.
Synonyms[1]
  • Poiretia J.F.Gmel. non Vent.
  • Panetos Raf.
  • Chamisme Nieuwl.

Bluets are often small and delicate. For example, H. rosea may grow only one inch tall. Some species are single stemmed and others have multiple stems in bunches. Flowers are blue, purple, lavender, white, or rose, often with shades of one color present in an individual population. Flowers have 4 sepals, colloquially denominated "petals", a salverform corolla with 4 lobes, and an inferior ovary. Some species exhibit heterostyly. The fruit is an often roughly cordate capsule enclosing many seeds and which usually dehisces via a suture across its apex.

Houstonia consists of 20 species native to North America.[2] Another 5 species are classified in the genus Stenaria; Houstonia without Stenaria is paraphyletic.[3] Close relatives of the genus are Oldenlandia microtheca and, more distantly, Arcytophyllum.[4]

Its members superficially resembles species of the genus Myosotis (Forget-me-nots), but are distinguished from the latter by having only 4 sepals (petals) instead of 5.

Species

Species accepted as of May 2014 are:[5]

  1. Houstonia acerosa (A.Gray) Benth. & Hook.f.: Chihuahua, Coahuila, Nuevo León, Tamaulipas, and San Luis Potosí and Texas and New Mexico, United States
  2. Houstonia biloba Raf.
  3. Houstonia caerulea L. (azure bluet): eastern Canada and eastern United States
  4. Houstonia canadensis Willd. ex Roem. & Schult. (Canadian summer bluet): Ontario and Saskatchewan, Canada and eastern United States
  5. Houstonia cervantesii Terrell
  6. Houstonia chlorantha Bertol.
  7. Houstonia correllii (W.H.Lewis) Terrell (Correll's bluet): Texas, United States
  8. Houstonia croftiae Britton & Rusby (Croft's bluet): Texas, United States
  9. Houstonia humifusa (Engelm. ex A.Gray) A.Gray (matted bluet): New Mexico, Oklahoma, and Texas, United States
  10. Houstonia longifolia Gaertn. (longleaf summer bluet): eastern and central United States and central Canada
  11. Houstonia micrantha (Shinners) Terrell (southern bluet): central and southeastern United States
  12. Houstonia nuttalliana Fosberg
  13. Houstonia ochroleuca Raf.
  14. Houstonia ouachitana (E.B.Sm.) Terrell (Ouachita bluet): Arkansas and Oklahoma, United States
  15. Houstonia palmeri A.Gray: Coahuila and Nuevo León
  16. Houstonia parviflora Holz. ex Greenm. (Greenman's bluet): Texas, United States
  17. Houstonia procumbens (J.F.Gmel.) Standl. (roundleaf bluet): Louisiana, Mississippi, Alabama, Georgia, Florida, and South Carolina, United States
  18. Houstonia prostata Brandegee
  19. Houstonia purpurea L. (Venus' pride): eastern and central United States
  20. Houstonia pusilla Schöpf (tiny bluet): central and southeastern United States and Arizona, United States
  21. Houstonia reticulata Raf.
  22. Houstonia rosea (Raf.) Terrell (rose bluet): south-central United States
  23. Houstonia rubra Cav. (red bluet): northern and central Mexico as far south as Puebla and Arizona, New Mexico, Texas, and Utah, United States
  24. Houstonia serpyllifolia Michx. (creeping, mountain, thymeleaft, and Appalachian bluet): Appalachian Mountains from Pennsylvania to Georgia, United States
  25. Houstonia sharpii Terrell: Hidalgo and Veracruz
  26. Houstonia spellenbergii (G.L.Nesom & Vorobik) Terrell: Chihuahua
  27. Houstonia subviscosa (C.Wright ex A.Gray) A.Gray (nodding bluet): Texas, United States
  28. Houstonia teretifolia Terrell: Coahuila
  29. Houstonia wrightii A.Gray (pygmy bluet): Arizona, New Mexico, and Texas, United States and Mexico

References
  1. "World Checklist of Selected Plant Families".
  2. Edward E. Terrell (10 June 1996), "Revision of Houstonia (Rubiaceae-Hedyotideae)", Systematic Botany Monographs, American Society of Plant Taxonomists, 48: 1–118, doi:10.2307/25027862, JSTOR 25027862
  3. Sheri A. Church; Douglas R. Taylor (2005), "Speciation and Hybridization among Houstonia (Rubiaceae) Species: The Influence of Polyploidy on Reticulate Evolution", American Journal of Botany, 92 (8): 1372–80, doi:10.3732/ajb.92.8.1372, PMID 21646157
  4. Groeninckx, I.; Dessein, S.; Ochoterena, H.; Persson, C.; Motley, T.J.; Kårehed, J.; Bremer, B.; Huysmans, S.; Smets, E. (2009). "Phylogeny of the Herbaceous Tribe Spermacoceae (Rubiaceae) Based on Plastid DNA Data". Annals of the Missouri Botanical Garden. 96 (1): 109–32. doi:10.3417/2006201. S2CID 56042261.
  5. Kew World Checklist of Selected Plant Families

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