Haloragaceae R.Br.

Haloragaceae, Hutchinson and Dalziel. Flora of West Tropical Africa 1:1. 1954

Morphology General Habit

Herbs or undershrubs, often aquatic; leaves alternate, opposite or verticillate, sometimes very large, the submersed ones often much divided; stipules absent

Morphology Reproductive morphology Flowers

Flowers hermaphrodite or unisexual, solitary to paniculate or corymbose, often very small

Morphology Reproductive morphology Flowers Calyx

Calyx-tube adnate to the ovary; lobes 2–4 or absent

Morphology Reproductive morphology Flowers Corolla

Petals 3–4 or absent, valvate or slightly imbricate

Morphology Reproductive morphology Flowers Androecium

Stamens 2–8, rarely 1, large; anther basifixed, 2-celled, opening lengthwise

Morphology Reproductive morphology Flowers Gynoecium

Ovary inferior, 1–4-celled; styles 1–4; ovules as many as the styles, pendulous from the apex of the cells

Morphology Reproductive morphology Fruits

Fruit small, a nut or drupe, sometimes winged, indehiscent or rarely breaking up into cocci

Morphology Reproductive morphology Seeds

Seeds pendulous, with copious endosperm and straight fairly large (rarely small) embryo

Every, J.L.R. (2009). Neotropical Haloragaceae.

Morphology

Description

Herbs, perennial or rarely annual (Myriophyllum L.), aquatic or amphibious, not free -floating, with adventitious nodal roots , exstipulate , with 1(-3) deciduous pseudostipules (hydathodes) present in leaf axils of Myriophyllum. Leaves heterophyllous (Proserpinaca L. and Myriophyllum), with submerged and emergent leaves differing, opposite, alternate , spiraling or whorled , entire or finely pinnately dissected , sometimes serrate and simple , shortly petiolate , subsessile or sessile . Inflorescence axillary , thyrses lacking terminal flowers (Proserpinaca) or racemes with female flowers in lower part and males in the upper (Myriophyllum) or 1-11-flowered fascicles, sometimes of either bisexual and female flowers or made up of both male and female (Laurembergia P. J. Bergius); bracteoles 2. Flowers, very small, actinomorphic , hermaphroditic, polygamous or unisexual and monoecious , epigynous , (2-)4- merous or 3- merous (Proserpinaca) sessile or pedicillate; sepals valvate , forming a tube, persistent (mostly absent in female Myriophyllum; petals absent or rudimentary and free , imbricate ; stamens (1-)4 or 8 (3 in Proserpinaca), filaments short, slender; anthers basifixed, dehiscing by slits; gynoecium (-2)4-carpellate; ovary inferior (-1)4-locular, sometimes becoming unilocular (Laurembergia), stylodia 1 per carpel , feathery, stigma capitate . Fruit non- fleshy , indehiscent or an ornamented schizocarp . Seeds 1-3.

Distribution

Distribution in the Neotropics

• Centre of diversity in Australia with c. 60% of species (Moody 2007).
• Three Neotropical genera grow in slow moving water or in marshy, littoral habitats.
• Some species are found at greater than 3,000 m.
• Myriophyllum is the most speciose genus of the family and has a cosmopolitan distribution and can be found in eastern South America, the West Indies and Central America.
• Proserpinaca has c. 3 species and occurs from North America through Mexico into Guatemala and the West Indies.
• Laurembergia is a pantropical genus (excluding Australia) with c. 4 spp. and widespread in the Neotropics particularly eastern South America.

Diagnostic

Distinguishing characters (always present)

• Aquatic or amphibian herbs.
• Axillaryinflorescence.
• Small flowers with radial symmetry.
• Anthers basifixed, dehiscing by longitudinal slits.
• Ovary inferior.
• Styles distinct and feathery.
• Stigmacapitate.
• Fruit non-fleshy.

Other important characters

• 2 bracteoles subtending the flower, occasionally caducous.
• Petals yellow, blue-green or red-purple.

Key differences from similar families

The features listed are not present in the Haloragaceae:

• Gunneraceae: petiolate (often long), zygomorphic flowers, fleshydrupaceous fruits or leathery dehiscent fruits.
• Penthoraceae: superiorovary, many seeds.
• Tertracarpaeaceae: superiorovary, free carpels, many seeds, endemic to Tasmania.

Notable genera and distinguishing features

Proserpinaca:

• Alternate heterophyllous leaves.
• Inflorescence solitary or in dichasia of up to 3 flowers per axil.
• Flowers hermaphroditic.
• Fruit 3-seeded nutlet.

Myriophyllum:

• Whorled heterophyllous leaves.
• Flowers frequently unisexual.
• Sepals less than half the length of the petals (frequently absent).
• Fruit schizocarpic, ornamented and splitting at maturity into 2-4 mericarps.

Laurembergia:

• Leaves subwhorled, opposite or alternate, not heterophyllous.
• Flowers unisexual in dichasia, the distal positions occupied by male or hermaphroditic flowers which stand out on a long pedicel from the almost sessile female flowers.
• 8 stamens in 2 whorls with the outer fertile whorl alternating with the sepals.
• The ovary initially 4-loculate, becoming 1-4-loculate through the collapse of the columella.
• One-seeded fruit with variable structure.

General Description

Status

• Native.
• Myriophyllum aquticum (Vell.) Verdc. and M. spicatum L. are invasive weeds.

General notes

• Anemophilous.
• Cultivated in aquaria and sometimes as pond plants.

Number of genera

• Three Neotropical representatives of the eight mainly antipodean genera.

Notes on delimitation

• Sister to the monogeneric Penthoraceae which does not occur in the Neotropics (Stevens, 2001 onwards).
• Placed within the Saxifragales (APG2, 2003).
• Removed from the Myrtales by Takhtajan (1997).
• Long associated with Gunneraceae.

Literature

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.

Brummitt, R.K. In Heywood, V.H., Brummitt, R.K., Culham, A. and Seberg, O. (eds). 2007. Flowering Plant Families of the World, pp. 162-3. Royal Botanic Gardens, Kew, Richmond.

Kubitzki, K. 2007. Haloragaceae. In: Kubitzki, K. (ed.). Families and genera of vascular plants. Volume 9. Flowering plants. Eudicots.pp.185-190. Springer-Verlag, Berlin.

Maas, P.J.M. & Westra, L.Y. Th. 2005. Neotropical Plant Families. 3rd ed, p.148. A.R.G. Gantner Verlag K.G., Ruggell.

Mabberley, D. J. 2008. Mabberley's Plant-book. 3rd ed. p. 387 Cambridge University Press, Cambridge.

Moody, M. L. & Les, D. H. 2007. Phylogenetic systematics and character evolution in the angiosperm family Haloragaceae. American Journal of Botany 94(12): 2005-2025.

Orchard, A. E. 1981. A revision of South American Myriophyllum (Haloragaceae), and its repercussions on some Australian and North American species. Brunonia 41: 27-65.

Smith, N. & Stevenson, D.W. 2004.  Haloragaceae. In: Smith, N., Mori, S.A., Henderson, A., Stevenson, D.W. and Heald, S.V. (eds). Flowering Plants of the Neotropics. pp.178-179. 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/.

Takhtajan, A. 1997. Diversity and Classification of Flowering Plants. Columbia University Press, New York.

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

Haloragaceae, R. Boutique (Jardin botanique national de Belgique) and B. Verdcourt (Royal Botanic Gardens, Kew). Flora of Tropical East Africa. 1973

Morphology Reproductive morphology Fruits

Fruit a nutlet or drupe, bluntly angular, ribbed or winged with 1–4 1-seeded locules or divided in 2 or 4 1-seeded cocci

Morphology Reproductive morphology Seeds

Seeds with abundant fleshy albumen

Morphology General Habit

Aquatic or terrestrial herbs or subshrubs with hermaphrodite, monoecious or dioecious flowers

Morphology Leaves

Leaves usually exstipulate, alternate, opposite, whorled or all radical, sometimes very small, the blades simple, entire or ± divided especially in the case of submerged leaves

Morphology Reproductive morphology Inflorescences

Inflorescences axillary or terminal, the flowers in cymes, fascicles, racemes, panicles, spikes or solitary; bracts often present

Morphology Reproductive morphology Flowers

Flowers often bracteolate, usually small, regular

Morphology Reproductive morphology Flowers Calyx

Calyx with the tube adnate to the ovary; lobes 2–4, valvate, sometimes rudimentary or absent

Morphology Reproductive morphology Flowers Corolla

Petals 2(–3)–4, valvate or slightly imbricate-contorted, or sometimes absent

Morphology Stem

Stems (1–)2–8; filaments long or short; anthers basifixed, 2-thecous, dehiscing by lateral slits

Morphology Reproductive morphology Flowers Gynoecium

Ovary inferior, rounded or angular to winged, 1–4-locular; locules 1-ovulate; ovule apical, pendulous, anatropous; styles 1–4, free or absent; stigmas papillate or plumose