Paul J.M. Maas & Hiltje Maas-van de Kamer
National Herbarium of the Netherlands (Wageningen branch), Wageningen, the Netherlands.
Description
Herbs, semi-aquatic, annual, somewhat succulent, glabrous. Leaves alternate, simple; stipules absent. Inflorescences dense, terminal, many-flowered spikes. Flowers bisexual, actinomorphic; sepals 5, connate at the base, imbricate, persistent; corolla urceolate to campanulate, 5-lobed, lobes imbricate; stamens 5, attached to the base of the corolla tube, filaments very short, anthers dithecal, longitudinally dehiscent; ovary inferior or perigynous, 2-locular, style 1, short or lacking, stigma 1, capitate, placentation axile, ovules many. Fruits membranous, circumscissile capsules. Seeds many, minute, striate.
Notes on delimitation
- The circumscription of the Sphenocleaceae is based on molecular studies. The family is currently placed in the order Solanales in the APG III system, most closely related to Hydroleaceae (formerly in Hydrophyllaceae) (Stevens, 2008; APG III, 2009).
- Cronquist (1981) and Takhtajan (2009) both placed the members of the family in the Campanulales.
- In the past it has also been placed near Phytolaccaceae by some authors.
Distribution in the Neotropics
- The family occurs pantropically and consists of one genus, Sphenoclea Gaertn., with two species, one pantropical species (S. zeylanica Gaertn.) - widespread throughout the Neotropics in wet, disturbed places like rice plantations and irrigation channels.
Distinguishing characters (always present)
- More or less succulent herbs of damp or flooded habitats.
- Leaves alternate, simple.
- Inflorescences dense, many-flowered spikes, more or less resembling the inflorescences of Phytolaccaceae and Piperaceae.
- Fruits membranous, circumscissile capsules.
Key differences from similar families
- Convolvulaceae differ from Sphenocleaceae in mostly being twining, having free sepals, and by never having spicate inflorescences.
- Solanaceae differ from Sphenocleaceae in never having spikes, and mostly having berries, drupes, or septicidal capsules, instead of membranous, circumscissile capsules.
- Sphenocleaceae differ from Phytolaccaceae in: the perianth consisting of both sepals and petals (Phytolacceae have only tepals); the inferior or perigynous ovary (Phytolaccaeae have a superior ovary); the circumscissile capsule (Phytolaccaeae have a berry or a drupe).
Status
- Sphenoclea is native to the Neotropics and the US.
Important literature
A.P.G. III. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Bot. J. Linnean Soc. 161: 105-121.
Brown, J.L. 2004. Sphenocleae. In: Smith, N.P., Mori, S.A., Henderson, A., Stevenson, D.W., and Heald, S.V. (eds.). Flowering plants of the Neotropics, pp. 357-358. Princeton University Press, Oxford and Princeton.
Cronquist, A. 1981. An integrated system of classification of flowering plants. Columbia University Press, New York
Jeppesen, S. 1981. Sphenocleaceae. In: Harling, G. & Sparre, B. (eds), Flora of Ecuador vol. 14, pp. 173-174. University of Gothenburg.
Maas, P.J.M. & Westra, L.Y.Th. 2005. Neotropical Plant Families. A concise guide of vascular plants in the Neotropics. 3rd ed., p. 283. A.R.G. Gantner Verlag K.G., Ruggell.
Souza, V.C. & Lorenzi, H. 2005. Botanica Sistemática. Guia ilustrado para identificação das famílias de Angiospermas da flora brasileira, baseado em APG II, p. 558. Nova Odessa, SP, Brasil.
Stevens, P.F. 2008. Angiosperm Phylogeny Website. Version 9 onwards. http://www.mobot.org/MOBOT/research/APweb/.
Takhtajan, A. 1997. Flowering Plants. Second edition. Springer Verlag, Berlin.
How to cite
Maas, P.J.M. & Maas-van de Kamer, H. (2012). Neotropical Sphenocleacae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Sphenocleacae.htm.
