Literature Cited

• Angiosperm Phylogeny Group (APG IV). 2016. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants:Botanical Journal of the Linnean Society. 181: 1-20.
• Angiosperm Phylogeny Group (APG III).2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: Botanical Journal of the Linnean Society. 161: 105-121.
• Angiosperm Phylogeny Group (APG II). 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: Botanical Journal of the Linnean Society. 141: 399-436.
• Angiosperm Phylogeny Group (APG). 1998. An ordinal classification for the families of the flowering plants. Annals of the Missouri Botanical Garden. 85: 531-553.
• Correll, D.S and M.C. Johnston, 1979. Manual of the vascular plants of Texas. University of Texas at Dallas, Richardson.
• Evans, Douglas B. 1998. Cactuses of Big Bend National Park. Univ. Texas Press, Austin.
• Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 12+ vols. New York and Oxford.
• Integrated Taxonomic Information System (ITIS) www.itis.gov
• Loflin B. & S. Loflin. 2009.Texas cacti. Texas A&M University Press. College Station.

• Morey, R. 2008. Little Big Bend. Texas Tech. University Press. Lubbock.

• Powell, A.M. 1998. Trees and shrubs of the Tras-Pecos and adjacent areas. Univ. Texas Press, Austin.

• Powell, A.M. 2000.Grasses of Trans-Pecos and adjacent areas. Iron Mountain Press, Marathon.

• Powell A.M. J.F. Weedin, and S.A. Powell. 2008. Cacti of Texas: a field guide. Texas Tech. University Press. Lubbock.

• West, S. 2000. Northern Chihuahuan Desert wildflowers. Falcon Publishing, Helena.