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Including Borboraceae Dulac (p.p.), Lilaeaceae Dum., Maundiaceae Nak., Triglochinaceae Dum.
Habit and leaf form. Herbs; laticiferous (rarely — Lilaea), or non-laticiferous, without coloured juice. Perennial (usually), or annual; with a basal aggregation of leaves; rhizomatous, or tuberous, or bulbaceous (very rarely). Hydrophytic, or helophytic (sometimes halophytic); of the hydrophytes, rooted. Leaves small, or medium-sized; alternate; spiral, or spiral to distichous (‘spirodistichous’); flat; sessile; sheathing. Leaf sheaths with free margins. Leaves with blades borne edgewise to the stem, or with blades ‘normally orientated’; simple; epulvinate. Lamina entire; linear (occasionally reduced to the sheath); parallel-veined. Leaves ligulate; stipulate, or exstipulate. Axillary scales present. Leaf development ‘graminaceous’.
Leaf anatomy. Stomata present; mostly paracytic. Lamina with secretory cavities (elongate canals). The mesophyll containing crystals, or without crystals. The crystals druses (?), or solitary-prismatic (? — crystals few, no raphides). Foliar vessels absent. Minor leaf veins without phloem transfer cells (Triglochin).
Axial (stem, wood) anatomy. Secondary thickening absent. The axial xylem without vessels.
Root anatomy. Root xylem with vessels; vessel end-walls scalariform.
Reproductive type, pollination. Unisexual flowers present. Plants dioecious, or polygamomonoecious. Pollination anemophilous.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes and in spikes. The ultimate inflorescence units racemose. Inflorescences scapiflorous; terminal; dense or sparse spikes and racemes. Flowers ebracteate; small; regular; 1 merous (Lilaea), or 2 merous, or 3 merous; cyclic. Perigone tube absent.
Perianth of ‘tepals’ (there being one member outside each stamen or staminode), or absent (if the ‘tepals’ are interpreted as staminal appendages — cf. Potamogetonaceae); 6 (usually), or 3, or 4, or 1; free; 2 whorled (usually), or 1 whorled; isomerous; sepaloid; without spots, or spotted (Tetroncium); similar in the two whorls.
Androecium 6 (usually), or 3 (when the inner whorl missing), or 8 (rarely), or 1 (rarely). Androecial members adnate (if the flower is interpreted as having a perianth); free of one another; 1 whorled, or 2 whorled ((4+4) 3+3 or 2+2, rarely only three or one). Androecium exclusively of fertile stamens, or including staminodes (alternate members sometimes sterile). Staminodes when present, 3, or 4. Stamens 3, or 6, or 8 (rarely); isomerous with the perianth, or diplostemonous; filantherous to with sessile anthers. Anthers dehiscing via longitudinal slits; extrorse; tetrasporangiate. Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Anther epidermis persistent. Microsporogenesis successive. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with one middle layer, or initially with more than one middle layer. Tapetum amoeboid. Pollen grains nonaperturate; 3-celled (Lilaea).
Gynoecium 6 carpelled, or 4 carpelled, or 1 carpelled. Carpels isomerous with the perianth. Gynoecium apocarpous, or syncarpous, or monomerous; eu-apocarpous to semicarpous, or synovarious (usually in two trimerous or dimerous whorls, the carpels usually adnate to the central axis but separating at maturity); superior. Carpel non-stylate, or stylate; apically stigmatic; 1 ovuled. Placentation basal (usually), or apical (Maundia). Gynoecium non-stylate, or stylate. Stigmas dry type; papillate; Group II type. Placentation basal to axile (usually), or apical (Maundia). Ovules 1 per locule; ascending (usually), or pendulous (Maundia); non-arillate; anatropous (usually), or orthotropous (Maundia); bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing only after one has been fertilized, or fusing simultaneously with the male gamete (?). Antipodal cells formed; 3; proliferating (Triglochin), or not proliferating (Lilaea); persistent (if only as vestiges). Synergids beaked. Endosperm formation nuclear. Embryogeny caryophyllad.
Fruit non-fleshy; an aggregate, or not an aggregate. The fruiting carpels if apocarpous, or considered so, coalescing into a secondary syncarp to not coalescing. The fruiting carpel dehiscent, or indehiscent; a follicle, or an achene. Fruit if syncarpous, a schizocarp. Mericarps 4, or 6; comprising achenes, or comprising follicles. Seeds non-endospermic. Seeds with starch. Cotyledons 1. Embryo straight. Testa without phytomelan; thin.
Seedling. Germination phanerocotylar. Hypocotyl internode absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling non-macropodous. Seedling cataphylls absent. First leaf centric. Primary root ephemeral.
Physiology, phytochemistry. Accumulated starch exclusively ‘pteridophyte type’. Cyanogenic, or not cyanogenic. Cynogenic constituents tyrosine-derived (triglochinin). Alkaloids absent. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent.
Geography, cytology. Frigid zone to sub-tropical. Widespread North and South temperate and frigid. X = 6, 8, 9.
Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Alismatiflorae; Zosterales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Alismatales.
Species 25. Genera 4; Triglochin (inc. Cycnogeton), Lilaea (~Triglochin), Maundia, Tetroncium.
General remarks. Lilaea is retained here following Dahlgren, Clifford and Yeo 1985 — but recognition of the family Lilaeaceae would greatly improve this description.
Illustrations. • Maundia triglochinoides: Das Pflanzenreich 16 (1903). • Tetroncium magellanicum: Das Pflanzenreich 16 (1903). • Tetroncium magellanicum: Hook. Ic. Pl. 2 (1832). • Le Maout and Decaisne: Triglochin. • Triglochin mucronata, as T. calcaratum: Hook. Ic. Pl. 5–6 (1842–3). • Le Maout and Decaisne: Triglochin, Tetroncium. • Le Maout and Decaisne: Lilaea. • Triglochin maritimum (B. Ent.). • Triglochin maritimum: Eng. Bot. 1434 (1869). • Triglochin palustre: Eng. Bot. 1433 (1869).
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: 4th May 2024. delta-intkey.com’.
