References
For Yucca
Clary, K.H. 1997. Phylogeny, character evolution, and biogeography of Yucca L. (Agavaceae) as inferred from plant morphology and sequences of the Internal Transcribed Spacer (ITS) region of the nuclear ribosomal DNA. The University of Texas at Austin, PhD dissertation. Google Scholar
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Hess, W.J., and R.L. Robbins. 2002. Yucca. In Flora of North America Editorial Committee. 2002a. Flora of North America north of Mexico. Volume 26, Magnoliophyta: Liliidae: Liliales and Orchidales. Oxford Univ. Press, New York, NY. 723 pp. Google Scholar
Keith, E.L. 2003. Yucca cernua (Agavaceae), a new species of Yucca from the series Rupicolae in Newton and Jasper counties in eastern Texas. Sida 21: 891-898. Google Scholar
McKelvey, S. D. 1947. Yuccas of the southwestern United States, Part II. The Arnold Arboretum of Harvard University, Jamaica Plain, MA. Google Scholar
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Verhoek, S. 1998. Agavaceae. Pp 60-70. In Kubitzki, K., ed. 1998a. The families and genera of vascular plants. III. Flowering plants – Monocotyledons – Lilianae (except Orchidaceae). Springer, Berlin. 478 pp. Google Scholar
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