Neotropical Crassulaceae

D.J. Nicholas Hind

Royal Botanic Gardens, Kew, UK. 

Description

Perennial herbs, rarely annual or biennial, rarely small shrubs, usually stem and/or leaf succulents. Leaves opposite or alternate, rarely verticillate, exstipulate, usually simple, usually glabrous, often glaucous, rarely with glands in leaf surface, sometimes pubescent, hairs either unicellular or multicellular and glandular-capitate or eglandular, margins usually entire, sometimes serrate, crenate or dentate, rarely coarsely lobed. Flowers usually in terminal cymose inflorescences, less often in spikes or racemes or solitary in leaf-axils, with or without bracts, regular, hermaphrodite, rarely unisexual and dioecious, mostly (3–)4–5 (–± 30)-merous; sepals 4–5 (–6), free or united into tube, persistent; petals same number as sepals, free or variously connate; stamens hypogynous or epipetalous, as many as petals or twice as many, in one whorl (Crassula-lineage) or more usually two whorls (Sedum-lineage), frequently obdiplostemenous, with outer whorl alternate and free from petals and inner whorl adnate to petals; filaments free or adnate to petals; anthers dorsifixed, bithecous, introrse, opening by a longitudinal slit; nectaries scale-like and usually present between the stamens and carpels. Carpels superior, equal in number to petals, free or slightly connate at base, unilocular; ovules (few–) many, inserted on adaxial suture, submarginal or proximally axile; styles short or elongated, stigmatic surface on inner side of apex. Fruit usually of separate follicles, rarely a capsule, follicles membranous or leathery, often surrounded by persistent membranous corolla, opening on adaxial side. Seed minute, glabrous, testa variously striate and sometimes ornamented with ridges or papillae; endosperm usually present and sparse; embryo straight.

Distribution in the Neotropics

  • Largest genus is Sedum L. with about 500 species in total.
  • Echeveria DC. is the largest in the Western hemisphere with c. 150 species.
  • Sedum follows Echeveria with c. 110 spp. in the Neotropics.
  • Crassula L. has c. 11 spp. in the Neotropics.
  • Villadia Rose contains c. 10 in Peru.

Number of genera

  • There are four native genera (Sedum, Echeveria, Crassula and Villadia) and one cultivated (Kalanchoe).

Useful tips for generic identification

  • Crassula spp. are usually prostrate or aquatic herbs, typically with isostemonous flowers.
  • Echeveria spp. have obovate fleshy leaves, usually arranged in a rosette, and lateral racemose inflorescences
  • Sedum spp. have paniculate cymes; both genera have free or basally connate petals.
  • There are several species of Kalanchoe that are cultivated, some naturalized; they are best recognized by flowers with (4) fused petals forming a tube, and many species have lobed, crenate or serrate margined leaves. A number of species of Kalanchoe, formally in the genus Bryophyllum, have plantlets on the leaf margins.

General notes

  • Main areas of speciation include Africa (dry areas), Madagascar, Macaronesia and Mexico.
  • Up to six subfamilies are recognized but following DNA analysis only two main lineages are seen clearly – the Crassula-lineage and the Sedum-lineage.
  • Mostly plants of dry, rocky habitats, usually terrestrial but rarely epiphytic and very rarely aquatic.

Important literature

Bywater, M. & G. E .Wickens. (1984). New World species of the genus Crassula. Kew Bull. 39(4): 699–728.

Claussen, R. T. (1959). Sedum of North America north of the Mexican Plateau. An exposition of taxonomic methods. Comstock Publishing Associates, Ithaca, New York. pp. 380.

Freire Fierro, A. (2004). Crassulaceae. In: G. Harling & L. Andersson (eds), Flora of Ecuador 73: 3-16. Botanical Institute, Göteborg University.

Fröderström, H. (1936). The genus Sedum L. : a systematic essay. Part. IV. Acta Horti Gotoburgensis. 10, Appendix. 1–181 + pl. I–CXV.

Pilbeam, J. (2008). The genus Echeveria. The British Cactus & Succulent Society, Hornchurch. 333 pp.

Walther, E. (1972). Echeveria. California Academy of Sciences, San Francisco. pp. 426.

How to cite

Hind, D.J.N. (2009). Neotropical Crassulaceae. 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/Crassulaceae.htm.