Scientific Name:
Trithuria inconspicua Cheeseman, Man. New Zealand Fl. 756 (1906)
  • Hydatella inconspicua (Cheeseman) Cheeseman, Trans. & Proc. Roy. Soc. New Zealand 39: 434 (1907)
Holotype: AK 2889, Sandy shores of Lake Ngatu, Waipapakauri, between Rangaunu Harbour and the West Coast, H. Carse s.n., Feb 1902
Not easily visible.

Aquatic perennial herb, tufted 10–55 mm in height, from a shortly branching erect rhizome, trichomes present; copious adventitious roots. Apomictic or sexual. Plants in populations often female only, or plants cosexual with unisexual or bisexual reproductive units. Leaf-bases weakly dilated (not sheathing), hyaline, toothed auricles present or absent; leaves spreading, glabrous, 8.0–55 × 0.25–0.6 mm; lamina linear-filiform, adaxially faintly compressed below, terete above, apex rounded with a hydathode. Reproductive units (3.5–)4–5(–7) mm long, on glabrous scapes, 1–5 per plant; involucral bracts 2–4(–7), sometimes dimorphic. Stamens 1–8, anthers 0.8–1.4 mm long, filaments 1–5 mm long (only T. inconspicua subsp. inconspicua); pollination syndrome anemophilous or gravitational autogamy. Carpels (2–)8–25, white to reddish, with multicellular stigmatic hairs of unequal length or reduced to a knobbly capitate head. Fruits 0.39–0.56 × 0.2–0.5 mm, beaked, deciduous from persistent stalks, pericarp thin and membraneous, smooth, indehiscent. Seed faintly reticulate, yellow-brown to red-brown with a darker apical cap (formed by an operculum).


Trithuria inconspicua is morphologically similar to T. filamentosa of Tasmania, its sister species in phylogenetic analyses with an estimated divergence of 0.5 Ma [0–1.1 Ma] (Iles et al. 2012, 2014). They share unique features in the genus such as: perennial life history (Pledge 1974), a fully aquatic habitat (Edgar 1966; Edgar 1970; Wells et al. 1998) and apomixis (Remizowa et al. 2008; Rudall et al. 2009; Smissen et al. 2019). Gruenstaeudl et al. (2017) discovered a difference in length in the plastid genomes between the two species >15 kbp and hypothesised a single expansion in the IR region.

1Stigmatic hairs approx. 1 mm long (Northland)T. inconspicua subsp. inconspicua
Stigmatic hairs reduced to a capitate head (Otago, Southland)T. inconspicua subsp. brevistyla

The minute tufts have narrow, linear leaves with a single mid-vein. The female inflorescence has mostly two or four bracts (sometimes more) that enclose a distinctive cluster of yellow to white or pinkish carpels, each attached to a stalk. Trithuria inconspicua is most similar vegetatively to Eleocharis pusilla if the creeping rhizome of the latter is buried in the substrate and missed in collection, but in that case T. inconspicua can be distinguished from it and species of Isoetes by having non-septate leaves. It differs from species of Centrolepis by having no leaf-sheaths, or if they are present they are very short and weak, whereas species of Centrolepis have a relatively well-defined leaf-sheath.


Disjunct between the South Island (provinces of Southland and Westland) and the North Island (province of North Auckland).

The apparent absence of Trithuria inconspicua sensu lato in Lake Monowai may be due to the artificial raising of the lake level by 2.8 m in 1926 for power generation, since it is present in other nearby lakes. Recent surveys have not relocated Trithuria inconspicua sensu lato previously reported from Lake Moke near Queenstown in Otago and Lake Brunner in Westland. There are no specimens to verify whether these reports are of T. inconspicua subsp. brevistyla.


Aquatic and growing in sediments in the shallows of permanent lakes, both warm-temperate coastal dune lakes (T. inconspicua subsp. inconspicua) and cool-temperate glacial lakes (T. inconspicua subsp brevistyla).

Indigenous (Endemic)
Number of subspecific taxa in New Zealand within Trithuria inconspicua Cheeseman
Indigenous (Endemic)2
Cheeseman, T.F. 1906: Manual of the New Zealand Flora. Government Printer, Wellington.
Cheeseman, T.F. 1907: Notice of the occurrence of Hydatella, a genus new to the New Zealand flora. Transactions and Proceedings of the Royal Society of New Zealand 39: 433–434.
de Lange, P.J.; Norton, D.A.; Courtney, S.P.; Heenan, P.B.; Barkla, J.W.; Cameron, E.K.; Hitchmough, R.; Townsend, A.J. 2009: Threatened and uncommon plants of New Zealand (2008 revision). New Zealand Journal of Botany 47: 61–96. [Nationally Vulnerable]
de Lange, P.J.; Norton, D.A.; Heenan, P.B.; Courtney, S.P.; Molloy, B.P.J.; Ogle, C.C.; Rance, B.D. 2004: Threatened and uncommon plants of New Zealand. New Zealand Journal of Botany 42(1): 45–76. [as Hydatella inconspicua (Cheeseman) Cheeseman]
de Lange, P.J.; Rolfe, J.R.; Barkla J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.N.; Ford, K.A.; Breitwieser, I.; Schönberger, I.; Hindmarsh-Walls, R.; Heenan, P.B.; Ladley, K. 2018: Conservation status of New Zealand indigenous vascular plants, 2017. New Zealand Threat Classification Series. No. 22. [Nationally Critical]
de Lange, P.J.; Rolfe, J.R.; Champion, P.D.; Courtney, S.P.; Heenan, P.B.; Barkla, J.W.; Cameron, E.K.; Norton, D.A.; Hitchmough, R.A. 2013: Conservation status of New Zealand indigenous vascular plants, 2012. New Zealand Threat Classification Series 3. Department of Conservation, Wellington. [Nationally Endangered]
Edgar, E. 1966: The male flowers of Hydatella inconspicua (Cheesem.) Cheesem. (Centrolepidaceae). New Zealand Journal of Botany 4: 153–158.
Edgar, E. 1970: 12. Centrolepidaceae. In: Moore, L.B.; Edgar, E. Flora of New Zealand. Vol. II. Indigenous Tracheophyta: Monocotyledones except Gramineae. Botany Division DSIR, Wellington. 79–85.
Ford, K.A.; Champion, P.D. 2019: Nymphaeales. In: Breitwieser, I.; Wilton, A.D. (ed.) Flora of New Zealand - Seed Plants. Fascicle 5. Manaaki Whenua Press, Lincoln.
Gruenstaeudl, M.; Nauheimer, L.; Borsch, T. 2017: Plastid genome structure and phylogenomics of Nymphaeales: conserved gene order and new insights in relationships. Plant Systematics and Evolution 303: 1251–1270.
Iles, W.J.D.; Lee, C.; Sokoloff, D.D.; Remizowa, M.V.; Yadav, S.R.; Barrett M.D.; Barrett, R.L.; MacFarlane, T.D.; Logacheva, M.D.; Rudall, P.J.; Graham, S.W. 2014: Reconstructing the age of the ancient flowering-plant family Hydatellaceae (Nymphaeales). BioMed Central Evolutionary Biology 14: 102.
Iles, W.J.D.; Rudall, P.J.; Sokoloff, D.D.; Remizowa, M.V.; MacFarlane, T.D.; Logacheva, M.D.; Graham, S.W. 2012: Molecular phylogenetics of Hydatellaceae (Nymphaeales): sexual-system homoplasy and a new sectional classification. American Journal of Botany 99: 663–676.
Pledge, D.H. 1974: Some observations on Hydatella inconspicua (Cheesem.) Cheesem. (Centrolepidaceae). New Zealand Journal of Botany 12(4): 559–561.
Remizowa, M.V.; Sokoloff, D.D.; Macfarlane, T.D.; Yadav, S.R.; Prychid, C.J.; Rudall, P.J. 2008: Comparative pollen morphology in the early-divergent angiosperm family Hydatellaceae reveals variation at the infraspecific level. Grana 47: 81–100.
Rudall, P.J.; Remizowa, M.V.; Prenner, G.; Prychid, C.J.; Tuckett, R.E.; Sokoloff, D.D. 2009: Nonflowers near the base of extant angiosperms? Spatiotemporal arrangement of organs in reproductive units of Hydatellaceae and its bearing on the origin of the flower. American Journal of Botany 96(1): 67–82.
Smissen, R.D.; Ford, K.A.; Champion, P.D.; Heenan, P.B. 2019: Genetic variation in Trithuria inconspicua and T. filamentosa (Hydatellaceae): a new subspecies and a hypothesis of apomixis arising within a predominantly selfing lineage. Australian Systematic Botany 32: 1–11.
Sokoloff, D.D.; Remizowa, M.V.; Macfarlane, T.D.; Rudall, P.J. 2008: Classification of the early-divergent angiosperm family Hydatellaceae: one genus instead of two, four new species and sexual dimorphism in dioecious taxa. Taxon 57(1): 179–200.
Wells, R.D.S.; Clayton, J.S.; de Winton, M.D. 1998: Submerged vegetation of Lakes Te Anau, Manapōuri, Monowai, Hauroko, and Poteriteri, Fiordland, New Zealand. New Zealand Journal of Marine and Freshwater Research 32: 621–638.