Neotropical Burmanniaceae

Hiltje Maas-van de Kamer and Paul J.M. Maas

National Herbarium, Wageningen University Branch, the Netherlands. 

Description

Small herbs, myco-heterotrophic ("saprophytic") and without chlorophyll, or sometimes autotrophic and with chlorophyll; rhizome mostly present, cylindrical, rarely tuberous, densely covered with scale-like leaves; roots filiform, glabrous. Stems mostly unbranched, variously coloured. Leaves alternate, sessile, simple, entire, in myco-heterotrophic species small and scale-like, in autotrophic species to rather large and often rosulate. Inflorescence a terminal, bracteate, lax to contracted, usually bifurcate, few- to many-flowered cyme, or reduced to 1 flower only. Flowers bisexual, actinomorphic, variously coloured; tepals arranged in 2 whorls, basally connate; floral tube mostly persistent, sometimes provided with longitudinal wings or ribs; tepals 6, very rarely 3 (Marthella Urb.), the outer ones often much larger than the inner ones; stamens 3, erect, inserted in the floral tube just below and opposite the inner tepals, filaments short, anthers dithecal, introrsely and transversely dehiscent, connective dilated; style 1, cylindric to filiform, equaling the floral tube, 3-branched at the apex, stigmas variously shaped, sometimes provided with filiform appendages; ovary inferior, 1-locular with axile placentation to 3-locular with parietal placentation, often with septal nectaries or with nectaries on top of the ovary; ovules many, anatropous. Fruit a capsule, longitudinally or transversely dehiscent by slits or valves, or irregularly opening by withering of the fruit wall. Seeds many, small and "dust-like", fusiform to subglobose.

Notes on delimitation

  • For notes on this aspect see Merckx (2008).

Distribution in the Neotropics

From the southern USA and Mexico in the North to S Brazil and N Paraguay in the South, also in the West Indian Islands:

  • Apteria Nutt. - From the southern USA to Bolivia, Paraguay and SE Brazil, also in the West Indies.
  • Burmannia L. - From the southern USA to northern Argentina, Bolivia, Paraguay and SE Brazil, also in the West Indies.
  • Campylosiphon Benth. - Throughout tropical South America.
  • Dictyostega Miers - From Mexico to Bolivia and SE Brazil.
  • Gymnosiphon Blume (including Cymbocarpa Miers) - Throughout the Neotropics.
  • Hexapterella Urb. - Northern South America and Trinidad.
  • Marthella - Trinidad.
  • Miersiella Urb. - Throughout tropical South America.

Distinguishing characters (always present)

Other important characters

  • All genera, except for most species of Burmannia, are myco-heterotrophic ("saprophytic") herbs without chlorophyll.
  • Reduced, scale-like leaves.

Key differences from similar families

  • Could be confused with Triuridaceae, both sharing alternate, scale-like leaves and being almost exclusively myco-heterotrophic ("saprophytic"), but Triuridaceae have flowers with many, free carpels ("apocarpous") and flowers are often unisexual.

Number of genera

  • Apteria (1 sp.).
  • Burmannia (19 spp.).
  • Campylosiphon (1 sp.).
  • Dictyostega (1 sp.)
  • Gymnosiphon (incl. Cymbocarpa) (16 spp.).
  • Hexapterella (2 spp.).
  • Marthella (1 sp.).
  • Miersiella (1 sp.).

Useful tips for generic identification

Key to the genera of Neotropical Burmanniaceae

1. Autotrophic ("non-saprophytic") herbs (B. tenella excepted) with green, often rosulate leaves; flowers tubular to salverform (2-25 mm long), distinctly winged or ribbed, the wings running from the top of the floral tube to the ovary. Throughout the Neotropics …Burmannia
1. Myco-heterotrophic ("saprophytic") herbs; flowers rarely ribbed to slightly winged … 2 

2. Tepals soon falling off, leaving a naked floral tube … 3
2. Tepals persistent … 4  

3. Outer tepals entire; stamens with a distinct filament; flowers salverform, white to purple, 5-14 mm long, basal part slightly winged to ribbed; capsule dehiscent by    withering of the wall between the  ribs. N South America and Trinidad …Hexapterella
3. Outer tepals 3-lobed; stamens without a filament; flowers salverform, white to pale yellow, 3-15 mm long, basal part rarely winged to ribbed; capsule longitudinally dehiscent or dehiscent by withering of the wall. Throughout the Neotropics …Gymnosiphon (incl. Cymbocarpa)

4. Flowers salverform, 16-28 mm long, purplish blue to white; rhizome tuberous; outer tepals as long as the inner ones. Tropical South America ... Campylosiphon
4. Flowers tubular, infundibular to campanulate; rhizome never tuberous; outer tepals longer than the inner ones … 5

5. Flowers campanulate to infundibular, 6-21 mm long, purple to white; filaments basally decurrent ino a crescent-shaped pouch, and bearing abaxially a 2-lobed wing. S USA and the Neotropics …Apteria
5. Flowers tubular, 2-9 mm long …6  

6. Flowers nodding, 2-9 mm long, white to purplish white, or pale yellow; small septal glands present. Mexico to Bolivia and SE Brazil … Dictyostega
6. Flowers erect, three 2-lobed glands present on top of the ovary...7

7. Inflorescence umbelliform; flowers 3-5 mm long, purple to white. Tropical Souh America … Miersiella
7. Inflorescence capitate; flowers 6-7 mm long, yellowish. Trinidad …Marthella

Notable genera and distinguishing features

  • Apteria: Very widely distributed from the southern USA in the North to southern Brazil and N Paraguay in the South; its only species (A. aphylla (Nutt.)Barnhart ex Small) is highly variable, particularly in its flower shape and size.
  • Burmannia: The most common genus in the family, easily recognizable by its often winged, strikingly coloured flowers and in mostly being autotrophic.
  • Gymnosiphon ("naked tube"): Notoriously difficult genus because its drops its tepals already in a very young stage.
  • Marthella: Only known from Mount Tucuche in Trinidad, its last collection dating from 1898 (!) and possibly extinct.

Status

  • All genera are native.

General notes

  • Most myco-heterotrophic plant groups in the Neotropics (incl. Thismiaceae and Triuridaceae) are poorly known and much additional field work needs to be conducted.

Important literature

Maas, P.J.M., H. Maas-van de Kamer, J.van Benthem, H.C.M. Snelders, and T. Rübsamen. 1986. Burmanniaceae. Flora Neotropica Monograph 42: 1-189.

Maas-van de Kamer, H. 1998. Burmanniaceae. In: K. Kubitzki (ed.), The families and genera of vascular plants 3: 154-164.

Merckx, V. 2008. Myco-heterotrophy in Dioscoreales. Systematics and Evolution. Pp. 1-217. Leuven, Belgium.

How to cite

Maas-van de Kamer, H. & Maas, P.J.M. (2009). Neotropical Burmanniaceae. 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/Burmanniaceae.htm.