Neotropical Parnassiaceae

Jon L.R. Every

Royal Botanic Gardens, Kew, UK. 

Description

Tiny (less than 2 cm broad) annuals or herbaceous perennials (Parnassia townsendii B.L. Rob), forming hemispherical tufts, caulescent or acaulescent, or rhizomatous (P. townsendii), golden brown-red tannin sacs visible in epidermis. Leaves simple, whorled in a basal rosette and/or alternate to subopposite, entire, glabrous, petiolate, margins entire or serrate (P. townsendii), venation acrodromous. Inflorescence 1-flowered (rarely 2) at ends of short, leafy, angular scape. Flowers bisexual, minute (Lepuropetalon spathulatum Elliott), appearing sessile in the basal rosette or terminal; calyx a campanulate, 5-ribbed floral cup, persistent; corolla (4-)5 or absent (L. spathulatum), inserted on rim of the calyx cup, linear, white, smaller than and alternating with sepal lobes, fimbricate (P. townsendii); stamens 5, antesepalous, free from perianth, staminodes 5, antepetalous or absent, anthers dehiscing longitudinally; ovary subinferior, superior (P. townsendii), syncarpous, carpels 3-4, 3-locular (1 in P. townsendii), styles 3-4 (1 in P. townsendii), short or absent. Fruit loculicidally dehiscent capsules.  Seeds numerous, minute.

Notes on delimitation

  • Treated here to include the Lepuropetalaceae.
  •  Zhang and Simmons asked the question 'Are Parnassiaceae the sister group of Celastraceae, or do they represent an early derived lineage within Celastraceae?' (Zhang & Simmons, 2006).

Distribution in the Neotropics

  • Lepuropetalon spathulatum can be found by looking very carefully in disturbed areas, growing amidst grasses and other small annual herbs, mosses and liverworts, some times in damp and often sandy soil and outcrops.
  • Parnassia townsendii is endemic to the western slopes of Sierra Madre Occidental of Chihuahua, Mexico.

Distinguishing characters (always present)

  • Herbs.
  • Tannin sacs visible as red lines or dots on the leaves and calyx, especially when dry.
  • Flowers hermaphroditic.
  • Calyx quincunical and persisting into fruit.
  • Syncarpous ovary.
  • Fruit a capsule.
  • Numerous tiny seeds.

Other important characters

  • Staminodes opposite the petals and alternating with the fertile stamen.
  • Flowers usually solitary, if not then paired.

Key differences from similar families

Number of genera

  • Two: the monotypic Lepuropetalon and a single species of Parnassia.

Useful tips for generic identification

Lepuropetalon spathulatum:

  • Small, annual herb ca. 2cm broad.
  • Winter-growing.
  • Blade 2-6mm long, spatulate.
  • Flowers inconspicuous.
  • Corolla small, sub -microscopic or absent.
  • Ovary sub -inferior.
  • 3-locular.

Parnassia townsendii:

Status

  • Parnassia townsendii is endemic to western slopes of Sierra Madre Occidental of Chihuahua, Mexico.
  • Lepuropetalon spathulatum is a native.

Important literature

APG 2. 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. Botanical Journal of the Linnean Society. 141: 399-436.

Berkov, A. 2004. Lepuropetalaceae. In: Smith, N., Mori, S. A., Henderson, A., Stevenson, D. W. & Heald, S. V. (eds.). Flowering Plants of the Neotropics. p. 214. The New York Botanical Garden, Princeton University Press, Princeton.

Bye, R. A. & Soltis, D. E. 1979. Parnassia townsendii (Saxifragaceae), a Mexican Endemic. The Southwestern Naturalist 24:2 pp. 209-222

Culham, A. 2007. In: Heywood, V.H., R.K. Brummitt, A. Culham and O. Seberg (eds). Flowering plant families of the world, pp. 243-4. Kew: Royal Botanic Gardens, Kew.

Maas, P.J.M. & Westra, L.Y. Th. 2005. Neotropical Plant Families. 3rd ed. p. 166. A.R.G. Gantner Verlag K.G., Ruggell.

Simmons, M.P. 2004. Parnassiaceae. In Kubitzki, K. (ed.), amilies and genera of vascular plants vol. 6. Flowering plants. Dicotyledons. pp. 291-296.  Springer-Verlag, Berlin.

Spongberg, S. A. 1972. The genera of Saxifragaceae in the Southeastern United States. Journal of the Arnold Arboretum 53:4. pp. 409-498.

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

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

Zhang, L. & Simmons, M.P. 2006. Phylogeny and delimitation of the Celastrales inferred from nuclear and plastid genes. Systematic Botany 31:1. pp. 122-137

How to cite

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