The genus Zantedeschia is native to southern Africa. There are several species and many hybrids in cultivation, all known by the common name, "Calla lily." They grow from tuberous roots, and have the typical Aroid Family inflorescence structure of a spike, called the spadix, carrying the actual male and female flower parts, which is surrounded by a funnel-shaped bract called the spathe. The spathe may be white, yellow, pink, or any of a multitude of other colors in the cultivars of commerce.
The species recognized include the following:
aethiopica, odorata, albomaculata (ssp. albomaculata and macrocarpa), rehmannii, jucunda, pentlandii, valida, and elliottiana (which last they say has never been found in the wild.)
Definitive articles on Zantedeschia species can be found in Veld & Flora and the South African Journal of Botany,
Y. Singh, A.E. van Wyk, and H. Baijnath, "Know Your Arums", Veld & Flora, vol. 81 (2), pp. 54-55 (June, 1995).
Singh, Y., Van Wyk, A.E. & Baijnath, H. 1996. "Taxonomic notes on the genus Zantedeschia Spreng. (Araceae) in southern Africa." S. Af. J. Bot. vol. 62(6): pp. 321-324.
Letty, C. 1973. "The genus Zantedeschia." Bothalia vol. 11: pp. 5-26.
Bulbous Plants of Southern Africa, by Neil du Plessis and Graham Duncan, Tafelberg Pub. Ltd., Cape Town (1989).
Bulbs for Warm Climates, by Thad M. Howard, University of Texas Press, Austin (2001).
Bulbs, Revised Edition, by John E. Bryan, Timber Press, Portland (2002).
Cape Bulbs, by Richard L. Doutt, Timber Press (1994).
RHS Manual of Bulbs, John Bryan and Mark Griffiths, Eds., Timber Press (1995).