Neotropical Frankeniaceae

Jon L.R. Every

Royal Botanic Gardens, Kew, UK. 

Description

Shrubs or subshrubs, evergreen or woody perennials of low stature, usually halophytic or gypsophilous with salt glands and often with simple, unicellular indumentum on stems, leaves and calyces.  Leaves up to 14mm in length, simple, opposite, decussate, sclerophyllous and ericoid, occasionally succulent, blade margins slightly to strongly revolute, sometimes fringed with short, soft trichomes, leaf sheath extending along petiole margins when petiolate, decussate when sessile, midvein inconspicuous to prominently abaxially raised; without stipules.  Inflorescence terminal, sometimes axillary, solitary or in few-to many-flowered dichasia; bracteoles 2 and often with 2 additional bracts, these often basally connate, subtending flowers, leaf like; peduncles usually absent.  Flowers actinomorphic, usually bisexual or rarely unisexual then gynodiocecious, sessile; calyx synsepalous, tubular, 4-5 (-6)-lobed, strongly ribbed; petals 4-5(-6), free, clawed; ligule or scale-like appendage present adaxillary at petal base; androecium with 3-6(-8) stamens, anthers often orange-red (3-5 staminodes present in pistillate flowers of F. triandra J. Remy); gynoecium with superior ovary, 3 united carpels, 1 locule, the style filiform with 3 branches; placentation basal-parietal, ovules (1-)3(-many).  Fruits glabrous, papery, loculicidally dehiscent capsules, surrounded by persistent calyx, brown to golden brown, white or yellow.  Seeds 1-8(-40) per fruit.

Notes on delimitation

  • Currently placed in the non-core Caryophyllales as sister family to the non-Neotropical Tamaricaceae (APG II, 2003) with which they share many similarities including capsular fruit and a straight embryo. 
  • Placed in the Violales by Cronquist, who recognized a third genus Anthobryum Phil. (= F . triandra) along with Frankenia L. and the monotypic Hypericopsis Boiss. which occurs only in Southern Iran.

Distribution in the Neotropics

  • Frankenia chilensis Presl: coastal areas of S Peru and N Chile, saline conditions.
  • F. triandra: an inland species, also found in S Peru and N Chile, NW Argentina and the Puna of Bolivia at 3,350-4,800m.

Two further species are found just outside the floristic area but are nonetheless worthy of a mention;

  • F. gypsophilia I. M. Johnst: Chihuahuan Desert in sections of Nuevo León, San Luis Potosí and Zacatecas, Mexico at 1,600-2,200 m. Restricted to gypseous soils.
  • F. margaritae Medrano: endemic and a dominant species of Nuevo León, found at 1,900m.

Distinguishing characters (always present)

Other important characters

  • Halophytic (gypsophilous in F. gypsophila).
  • Bisexual (unisexual in F. triandra - gynodiocecious).
  • Dwarf, evergreen habit (F. triandra forms dense hard cushions only a few cm high).
  • Petiolate (except in F. gypsophila).
  • Peduncles absent (except F. chilensis)
  • Bracteolate; bracteoles 2 and distinct (F. triandra), or often 2 with 2 additional bracts, these often basally connate, subtending the flowers and leaf like.
  • Calyx synsepalous and tubular (or campanulate to urceolate in F. triandra).
  • Fruit white or yellow (brown to golden brown F. chilensis).

Key differences from similar families

Differs from Plumbaginaceae in having:

Number of genera

  • One genus Frankenia L. with two Neotropical and two Mexican species.

Status

Native.

General notes

  • Known as the "Revolver flowers" due to the prominent ligules which project inward, dividing the inner portion of the flower into separate compartments.
  • Frankenia was named after J. Franke, professor of botany at Uppsala.

Important literature

APG II, 2003. An update of the Angiosperm Phylogeny group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141(4): 399-436.

Heywood, V.H., R.K. Brummitt, Culham, A. and Seberg, O. (eds.). Flowering plant families of the world, p.150-1. Kew: Royal Botanic Gardens, Kew.

Maas, P. J. M. & Westra, L. Y. Th. 2005. Neotropical Plant Families. 3rd ed. P. 132. A.R.G. Gantner Verlag K.G., Ruggell.

Smith, N. 2004. Frankeniaceae. P. 163. In: Smith, N., Mori, S. A., Henderson, A., Stevenson, D. W. and Heald, S. V. (eds.). Flowering Plants of the Neotropics. The New York Botanical Garden, Princeton University Press, Princeton.

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

Watson, L. and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000.

Whalen, M. A. 1987. The systematics of Frankenia (Frankeniaceae) in North and South America. Systematic Botany Monographs. Vol. 17. The American Society of Plant Taxonomists.

 

How to cite

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