Neotropical Chloranthaceae

Jon L.R. Every

Royal Botanic Gardens, Kew, UK. 

Description

Evergreen trees (2-30 m tall) and scandent shrubs, large prop roots regularly present, glabrous or with non-glandular trichomes, all parts strongly aromatic. Leaves simple, opposite, decussate, petiolate, petiolar bases form a cylindric or quadrangular persistent sheath around the stem, nodes swollen; blade fleshy to coriaceous, pinnately veined, margins crenate-serrate; stipules 4. Staminate inflorescence in dioecious species (axillary or terminal, 1 to several spikes, axis racemose or paniculate; leaf-like bracts present), in monoecious species (solitary spikes on pistillate inflorescence axis or within a cymules (along with pistillate flowers)). Pistillate inflorescence axillary or terminal, cymules, spikes, racemes or panicles; bracts present. Staminate flowers basic, 60-300 flowers per spike, without perianth, ebracteate, 1-3 sessile stamens, anthers, oblong, longitudinally dehiscent. Pistillate Flowers simple, perianth lobes 0.5-3mm, free at the base or partially to completely united forming a small tube, adnate to the ovary; ovary inferior or semi-inferior, sometimes nude, carpel 1, locule 1, stigma 1 sessile or on very short style. Fruit a drupe, fleshy, aromatic and brightly coloured, exocarps thin, mesocarp fleshy, endocarp hard, or multiple with colourful, juicy floral bracts. Seed 1 per fruit, small, brown or black smooth or minutely papillate, endosperm well developed, oily.

Notes on delimitation

  • Chloranthaceae are probably sister to magnoliids (Moore et al. 2007) as the only family in the order Chloranthales.

Distribution in the Neotropics

  • Growing throughout the Neotropics, predominantly in wet, cool, montane forest at altitudes anywhere between 500m and 3,000m.
  • Two-thirds of the species are found in Andean South America, primarily in disturbed sites.

Distinguishing characters (always present)

  • Swollen leaf sheath in-between leaf stalks.
  • Unisexual flowers.
  • Minute perianth.
  • Opposite leaves.
  • Crenate to serrate leaf margins.
  • NB! Pungent odour from all broken parts of the plant.

Other important characters

  • Prop roots.
  • Floral bracts becoming colourful and succulent and appealing to birds.
  • Long flowering season.
  • Long staminate inflorescences with abundant pollen.

Key differences from similar families

Number of genera

  • One: Hedyosmum Sw. with 44 species.

Status

Native.

General notes

  • Hedyosmum brasiliense has medicinal property.
  • One species H. mexicanum C. Cordem. provides edible, sweet tasting fruit.
  • Hedyosmum is derived from the Greek words hedy (pleasant) osmum (smelling).
  • An interesting family from an evolutionary point of view, lending its name to the Chloranthoid Hypothesis, which suggests that the first flowering plants had the similar small, basic, unisexual, wind-pollinated flowers.

Important literature

Maas, P. J. M. & Westra, L. Y. Th. 2005. Neotropical Plant Families. 3rd ed. P. 106. A.R.G. Gantner Verlag K.G., Ruggell.

Moore et al. 2007. Using plastid genome-scale data to resolve enigmatic relationships among basal angiosperms PNAS: 104(49).

Todizia, C. A. 1988. Chloranthaceae: Hedyosmum. Flora Neotropica. Monograph 48. The New York Botanical Garden, New York.

How to cite

Every, J.L.R. (2009). Neotropical Chloranthaceae. 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/Chloranthaceae.htm.