Neotropical Casuarinaceae

Description

Evergreen trees and shrubs, slender, with wiry, jointed and grooved branches with quadrangular segments. Leaves reduced into simple, sessile scales grouped in whorls of 4-20, these surrounding the articulations, indumentum of simple or branched trichomes, plants rarely glabrous. Inflorescences indeterminate, catkins, (male flowers terminal, female flowers in a globose heads on side branches). Flowers unisexual (plants monoecious or dioecious), reduced, radially symmetrical, bracteate and with 2 bracteoles, tepals inconspicuous. Staminate flowers grouped together along the spike, stamen 1, free of perianth, anthers basifixed, dehiscing by longitudinal valves. Pistillate flowers naked, ovary superior, syncarpous, carpels 2, bilocular, styles 1-2, short. Fruits of adjoining bracteoles and perianth forming a multiple cone-like infructescence of samaroid nuts. Seeds 1.

Notes on delimitation

• Placed in the Fagales, sister to Betulaceae and Myricaceae (APG III, 2009).

Distribution in the Neotropics

• Introduced and naturalised throughout the Neotropics.

Distinguishing characters (always present)

• Highly reduced scale-like leaves.
• One stamen.
• Multiple infructescence formed by enlarged and thickened bracteoles and perianth.
• Fruit black and shiny with slightly raised wavy lines.

Key differences from similar families

• Superficially and vegetatively Casuarianaceae resemble gymnosperms or Equisetum L., but the Angiosperm flowers set them apart.

Number of genera

• One genus: Casuarina L.
• Two species: Casuarina equisetifolia L. and C. cunninghamiana Miq.
  

Status

• Naturalised.

General notes

• Nitrogen-fixing roots.
• Commonly known as the She-Oak Family and Beefwoods.
• A global noxious weed.
• Wind pollinated and dispersed, but an important source of firewood and construction materials for some communities.

Important literature

APG III. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. Bot. J. Linn. Soc. 161(3): 105-121.

Jury, S.L. 2007. Casuarinaceae, pp. 91-92. In: Heywood, V.H., R.K. Brummitt, A. Culham and O. Seberg (eds.). Flowering Plant Families of the World. Royal Botanic Gardens, Kew.

Judd, W.S., Campbell, C.S., Kellogg, E.A., Stevens, P.F. and Donoghue, M.J. 2008. Plant Systematics: a phylogenetic approach 3rd ed. Sinauer Associates, Massachusetts. Pp 387-389.

Johnson, L.A.S. and Wilson, K.L. 1993. Casuarinaceae, pp. 237-242. In: Kubitzki, K (ed.). The Families and Genera of Vascular Plants. Vol II. Springer-Verlag, Berlin.

Stevens, P. F. 2008. Angiosperm Phylogeny Website. Version 9 onwards. http://www.mobot.org/MOBOT/research/APweb/

Watson, L. and Dallwitz, M.J. 1992 onwards. The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version 3rd March 2009. http://delta-intkey.com

Wilmot-Dear, C. M.1991. Flora Zambesica, vol 9: part 6, p. 116., Royal Botanic Gardens, Kew.