Neotropical Hypoxidaceae

Julie H. A. Dutilh

Universidade Estadual de Campinas (Unicamp), Campinas, Brazil. 

Description

Perennial geophytes, sparcely to densely pubescent, with a vertical rhizome often surrounded with fibers of old leaves. Leaves rosulate, sessile, flat, with prominent parallel veins. Inflorescences often several, generally on a scape, scape sometimes very short and subterranean, umbel-like, with 1-3 pedicellate to sessile flowers subtended by bracts; pedicel not articulate. Flowers hermaphrodite, actinomorphic; tepals 6, in two whorls apparent or not, petaloid, free, yellow, 3 outer ones sometimes greenish and pubescent on abaxial side; stamens 6 opposite tepals with sagittate anthers; filaments inserted on the base of the tepals; ovary inferior, tri-carpellate and tri-locular, sometimes unilocular maybe due to incomplete septa, several ovules per locule; style at apex of ovary, solitary, erect; stigma capitate, trilobate. Fruit capsule with irregular dehiscence, or fleshy, with 1- several seeds per locule. Seeds black, more or less globose.

Notes on delimitation

  • The family Hypoxidaceae, its genera and species have a complex taxonomic history, not yet fully understood.
  • The family Hypoxidaceae was considered by Rudall (2003) to have a close morphological relationship with Orchidaceae. It is now considered to be close to Asteliaceae and Lanariaceae.
  • In the family Hypoxidaceae, species from genera Hypoxidia Friedmann and Spiloxene Salisb. have intermediate ovary between trilocular and unilocular.
  • Ravenna created genus Heliacme Ravenna (based on Curculigo scorzonerifolia Lam.) for the Neotropics, on the basis of  a unilocular ovary and dry fruit (as compared with the rest of Curculigo Gaertn. which is otherwise African). But the fruit is not dry, and the ovary remains yet to be better understood in the genus.

Distribution in the Neotropics

  • The largest genus of the family is Hypoxis L., but this has many taxonomic problems with delimitation of its species, as they have a high degree of apomixy. It is found in tropical and subtropical areas of all continents.
  • The family is found mainly in Africa, but Hypoxis and Curculigo have a few native species in the Neotropics.

Number of genera

  • Two in the Neotropics: Hypoxis and Curculigo.

Useful tips for generic identification

  • Hypoxis is characterized by the aerial flower scape and dry fruit, and Curculigo by the subterranean ovary and fleshy fruit.
  • Curculigo has only one known species in the Neotropics, which has a flower that appears at ground level and subterranean fruits.  C. scorzonerifolia (Lam.) Baker is characterized by the umbel with a sessile or almost sessile flower.

Important literature

Nordal, I. (1998). Hypoxidaceae. Pp. 286-295. In: Kubitzki, K. (ed.), The Families and Genera of Vascular Plants: Monocotyledons - Lilianae (except Orchidaceae). Springer-Verlag, Berlin.

Ravenna, P. (2003). Heliacme Ravenna, a new genus of New World Hypoxidaceae. Onira 8(2): 5-9.

Seubert, M. (1847). Hypoxideae. Pp. 48-52. In Martius, CFP. Flora Brasiliensis. Lipsiae

How to cite

Dutilh, J.H.A. (2009). Neotropical Hypoxidaceae. 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/Hypoxidaceae.htm.