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Common name: Hydatella Family.
Number of genera 2. Number of species 7.
Angiosperm. Liliopsida.
Disseminule a dehisced fruit, or an intact or entire fruit, or a seed.
Fruits
Pistil(s) compound; 1; 1-pistillate; with carpels united. Fruit anthocarp; compound; follicular anthecetum (Trithuria Spjut has 3 families: Centrolepidaceae, Hydatellaceae & Poaceae.); without persistent central column; within accessory organ(s), or not within accessory organ(s); within calyx (Hydatella); accrescent; persistent; per fruit 1-seeded, or many-seeded (but many per female head); 1-seeded (per fruit, but many per female head); less than 1 cm long; 0.04–0.05 cm long; 3-carpellate (assumed); with carpels separate (essentially); with carpels separating at maturity (assumed); without sterile carpels; not sulcate; in transection terete (more or less); apex not beaked; wall chartaceous (per fruitlet - but many carpels in fruiting head); dehiscent (Trithuria), or indehiscent (Hydatella). Dehiscent unit seed(s). Dehiscent regularly; passively; at base to apex (& remaining attached); and shedding seeds; with replum, or without replum; fruit without centered partition attached to replum. Epicarp brown (all shades) (including pale, greenish, or whitish); durable; membranous; glabrous (without hairs); without armature; smooth, or not smooth; wrinkled; without wing(s); without apical respiratory hole. Mesocarp absent. Endocarp present, or absent; not separating from exocarp; thin; not splitting into 1-seeded pyrenes; smooth; without wing; without operculum; without secretory cavities; without mechanism for seedling escape; without grooves; without longitudinal ridges. Funiculus short; short without seed bearing hooks (retinacula); not persisting in fruit after seed shed.
Seeds
Aril absent. Seed minute; 0.3–0.4 mm long; not bowl shaped; not nutlike; without winglike beak; without caudate appendage(s); at maturity with food reserves; with perisperm, or endosperm (as a trace); without canavanine. Sarcotesta absent. Testa present; without markedly different marginal tissue; without fleshy or leathery layer over hard layer; tight; surface smooth, or unsmooth; surface with merged raised features; surface reticulate, or sculptured, or wrinkled; without crease or line separating cotyledons from hypocotyl-radicle; without notch along margin where cotyledons from hypocotyl-radicle tip approach each other; without glands; without bristles; glabrous; without wings; without collar; with operculum (no mention of a collar); transparent (with a dark tip); monochrome; brown (all shades); not becoming mucilaginous when wetted; surrounding food reserve. Hilum punctate (assumed). Endosperm development cellular; trace; more limited than sheath around radicle.
Perisperm copious; with starch; opaque. Embryo scarcely differentiated from food reserve, or undifferentiated from food reserve; well developed, or rudimentary; 1 per seed; partially filling testa (with food reserve); 0.1 times the length of food reserve (estimated); at one end of seed not extending into a depression or cup; peripheral; miniature; lenticular; lenticular; without coleoptile; without coleorhiza; without simmondsin; without stomata; not green; acotyledonous, or with 2 or more cotyledons. Cotyledons barely 2; equal in size; not punctate dotted. Hypocotyl-radicle undeveloped.
Distribution
Old World. Australia, Oceania (1 species in New Zealand).
Weed information
No USA noxious weeds.
Listed seeds
No ASOA or ISTA listed seeds.
Accepted genera
Hydatella Diels -- Trithuria Hook. f.
References specific to this family
Cronquist page 1148. Hamann, U. 1976. Hydatellaceae - a new family of Monocotyledoneae. New Zealand J. Bot. 14:193–196; Diels, L. & E. Pritzel. 1904. Fragmenta Phytographiae Australiae occidentalis. Bot. Jahrb. 35:55–662.
General references
Cronquist, A. 1981. An integrated system of classification of flowering plants, 1,262 p. Columbia University Press, New York, Engler, A. 1900–1953. Das Pflanzenreich, nos. 1–107. Facsimile edition. Engelmann-Cramer, Weinheim, Flora of Australia (various years and volumes). Australian Government Publication, Canberra, Gunn, C.R., J.H. Wiersema, C.A. Ritchie, and J.H. Kirkbride, Jr. 1992 and amendments. Families and genera of Spermatophytes recognized by the Agricultural Research Service. Techn. Bull. U.S.D.A. 1796:1–500, Hooker, J.D. 1873 and forward. Icones Plantarum. William & Norgate, London. (plate number cited in text within [ ]), Mabberley, D.J. 1987. The plant-book, 706 p. Cambridge University Press, Cambridge, Spjut, R.W. 1994. A systematic treatment of fruit types. Mem. New York Bot. Gard. 70:1–182.
Illustrations
Acceptable fruit and no seed illustrations. Cronquist has no illustration. Disseminule illustration(s): fruit. Fruit illustration(s): Diels & Pritzel (1904–5), Flora of Australia (various volumes), Morley & Toelken, Hooker [1858].
• Fruit. 1 of 3. Hydatella filamentosa (Rodway) W. M. Curtis: dehisced fruit. • Seed. 2 of 3. Hydatella filamentosa (Rodway) W. M. Curtis: seeds. • Embryo. 3 of 3. Trithuria submersa Hook. ex Moq.: embryo.
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, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘J.H. Kirkbride, Jr., C.R. Gunn, and M.J. Dallwitz. 2000 onwards. Family guide for fruits and seeds: descriptions, illustrations, identification, and information retrieval. Version: 12th April 2021. delta-intkey.com’.
