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The families of flowering plants

L. Watson and M.J. Dallwitz

Haloragidaceae R. Br.

Alternatively Haloragaceae R. Br.

Including Cercodianae (Cercodiaceae) Juss., Halorrhageae (Halorrhagaceae) Lindl., Myriophylleae (Myriophyllaceae) Schultz-Schultzenst.; excluding Gunneraceae.

Habit and leaf form. Herbs (mostly), or shrubs, or ‘arborescent’ (Haloragodendron). Plants non-succulent; green and photosynthesizing. Stem growth not conspicuously sympodial (monopodial). Hydrophytic to helophytic, or mesophytic; the aquatics rooted. Leaves of hydrophytes submerged and emergent. Heterophyllous (aquatic members with submerged leaves dissected and emergent leaves more or less entire), or not heterophyllous (when not aquatic). Leaves alternate, or opposite, or whorled; when alternate, spiral; petiolate to sessile; non-sheathing; very varied in form, simple, or compound; epulvinate; when compound, pinnate. Lamina dissected, or entire; when simple/dissected, pinnatifid, or palmatifid (sometimes trifid); one-veined, or pinnately veined. Leaves exstipulate; becoming compound from primordial lobes.

Leaf anatomy. Stomata commonly on both surfaces; usually anomocytic. The mesophyll containing crystals. The crystals druses. Minor leaf veins without phloem transfer cells (1 genus).

Axial (stem, wood) anatomy. Primary vascular tissues much reduced in aquatics, being represented in Myriophyllum by an axile fibro-vascular mass with no pith; otherwise in a cylinder, without separate bundles (exemplified in Haloragis and Loudonia), or consisting of scattered bundles (polystelic in Gunnera, with variously orientated, separate steles). Secondary thickening absent, or anomalous (?).

The vessel end-walls simple.

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or polygamomonoecious. Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in spikes (commonly), or in corymbs (Loudonia), or in racemes. Inflorescences pseudanthial (at least, some forms sometimes considered so), or not pseudanthial. Flowers bracteolate (often), or ebracteolate; minute to small; regular (usually); (2–)4 merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium absent.

Perianth with distinct calyx and corolla, or sequentially intergrading from sepals to petals, or vestigial to absent; when present, 4, or 8; free; 2 whorled, or 1 whorled (C sometimes absent); isomerous. Calyx 2, or 4; 1 whorled; polysepalous; regular; persistent; valvate. Corolla when present, 2, or 4; 1 whorled; polypetalous; regular.

Androecium 8, or (3–)4. Androecial members free of the perianth; all equal; free of one another; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens 3–4, or 8; isomerous with the perianth, or diplostemonous; alternisepalous (when two-whorled), or oppositisepalous; filantherous (with rather large anthers). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; latrorse; tetrasporangiate; appendaged (apiculate), or unappendaged. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. Anther wall of the ‘monocot’ type. Pollen grains aperturate; colpate (sometimes rupoidate); 3-celled (in Myriophyllum).

Gynoecium (2–)3–4 carpelled. The pistil 1 celled, or 3–4 celled. Gynoecium syncarpous; synovarious; inferior. Ovary (1–)3–4 locular (partitions sometimes incomplete, pseudomonomeric in Glischrocaryon). Epigynous disk absent. Gynoecium stylate. Styles (2–)3–4 (feathery); free; apical. Stigmas dry type; papillate; Group II type. Placentation apical. Ovules in the single cavity (Glischrocaryon) 4; 1 per locule; pendulous; anatropous; bitegmic; crassinucellate. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids with filiform apparatus.

Fruit non-fleshy; indehiscent, or a schizocarp. Mericarps when schizocarpic, 2–4; comprising nutlets (e.g. Myriophyllum). Fruit when non-schizocarpic, a drupe, or a nut. The drupes with separable pyrenes, or with one stone. Seeds more or less copiously endospermic. Endosperm oily. Cotyledons 2. Embryo achlorophyllous (1/1); straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Anatomy non-C4 type (Myriophyllum). Cyanogenic. Iridoids not detected. Saponins/sapogenins present (in Haloragis), or absent. Proanthocyanidins present, or absent (Myriophyllum). Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid present (Haloragis, Myriophyllum).

Geography, cytology. Temperate to tropical. Cosmopolitan. X often = 7.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Haloragales. Cronquist’s Subclass Rosidae; Haloragales. APG III core angiosperms; core eudicot; unplaced at Superordinal level. APG IV Order Saxifragales.

Species 120. Genera 8; Glischrocaryon, Gonocarpus, Haloragis, Haloragodendron, Laurembergia, (Loudonia), Meziella, Myriophyllum, Proserpinaca.

Economic uses, etc. Myriophyllym is grown in ponds and aquaria, and important in limnological conservation.

Illustrations. • Gonocarpus teucrioides (as Haloragis): Hooker, Fl. Tasmaniae (1860). • Gonocarpus serpyllifolius (as Goniocarpus): Hook. Ic. Pl. 3 (1840). • Gonoarpus cordiger, as Haloragis cordigera: Hook. Ic. Pl. 5–6 (1842–3). • Le Maout and Decaisne: Haloragis. • Laurembergia cooperi: Thonner. • Loudonia aurea: Lindley. • Myriophyllum alterniflorum: Eng. Bot. 515 (1865). • Myriophyllum integrifolium and M. pedunculatum: Hooker, Fl. Tasmaniae (1860). • Myriophyllum spicatum: Eng. Bot. 514 (1865). • Myriophyllum verticillatum: Eng. Bot. 513 (1865). • Myriophyllum verticillatum (B. Ent.).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 5th March 2018.’.