Hydatellaceae are a family of small, aquatic flowering plants. The family consists of tiny, relatively simple plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges, but has been reassigned to the order Nymphaeales as a result of DNA and morphological analyses showing that it represents one of the earliest groups to split off in flowering-plant phylogeny, rather than having a close relationship to monocots, which it bears a superficial resemblance to due to convergent evolution. The family includes only the genus Trithuria, which has at least 13 species, although species diversity in the family has probably been substantially underestimated.
Trithuria is a genus of small ephemeral aquatic herb that represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. All 13 described species of Trithuria are found in Australia, with the exception of T. inconspicua and T. konkanensis, from New Zealand and India respectively. Until DNA sequence data and a reinterpretation of morphology proved otherwise, these plants were believed to be monocots related to the grasses (Poaceae). They are unique in being the only plants besides two members of Triuridaceae in which the stamens are centred and surrounded by the pistils; in Hydatellaceae the resulting 'flowers' may instead represent condensed inflorescences or non-flowers.
Haloragis erecta, the shrubby haloragis, toatoa or erect seaberry, is a plant species that is endemic to New Zealand.
Melicytus lanceolatus, commonly called narrow-leaved māhoe or māhoe-wao, is a small tree in the family Violaceae that is endemic to New Zealand.
Elatostema rugosum is an herbaceous dicot that is considered to be a groundcover. It is commonly called parataniwha, paratāniwhaniwha, New Zealand begonia, and begonia fern. It tends to grow in large masses. Although it has hairs and is in the nettle family, it does not possess any stinging hairs.
Disphyma australe is a species of flowering plant in the family Aizoaceae and is endemic to New Zealand. It is a prostrate, succulent annual shrub or short-lived perennial plant with stems up to 2 m long, leaves that are three-sided in cross-section with a rounded lower angle, and white to deep pink daisy-like flowers that are 2–4 cm (0.79–1.57 in) in diameter with 3–5 rows of petals and multiple stamens. Disphyma australe is a coastal plant and therefore can be found at cliff faces, gravel beaches, salt meadows and estuaries.
Trithuria inconspicua is a small aquatic herb of the family Hydatellaceae that is only found in New Zealand.
Myrsine divaricata also known as weeping māpou or weeping matipo, is a small tree up to 4 metres (13 ft) tall or often a shrub. It has a strongly divaricating habit with interlaced branches. The woody parts are stiff and pubescent when young. The small leathery simple leaves are borne on short petioles and may be slightly two lobed at the end. The very small yellow or reddish flowers may be borne singly or in small groups which mature into small purple, occasionally white, fruit.
Cardamine depressa, commonly known as bitter cress, is a plant in the Brassicaceae family, found in the Antipodean Islands.
Myosotis brockieisubsp. brockiei is a subspecies of flowering plant in the family Boraginaceae, endemic to southern South Island of New Zealand. Lucy Moore and Margaret Simpson described M. brockiei in 1973. Plants of this subspecies of forget-me-not are perennial rosettes which form caespitose tufts or clumps, with ebracteate, erect inflorescences, and white corollas with exserted stamens.
Myosotis traversiisubsp. traversii is a subspecies of flowering plant in the family Boraginaceae, endemic to the northern South Island of New Zealand. Joseph Dalton Hooker described the species M. traversii in 1864. Plants of this subspecies of forget-me-not are perennial rosettes which form tufts or clumps, with ebracteate, erect inflorescences, and white or yellow corollas with partly exserted stamens.
Myosotis pansa subsp. praeceps is a subspecies of flowering plant in the family Boraginaceae, endemic to the North Island of New Zealand. Lucy Moore described the variety M. petiolata var. pansa in 1961, and it was transferred to a subspecies of M. pansa by Heidi Meudt, Jessica Prebble, Rebecca Stanley and Michael Thorsen in 2013. Plants of this species of forget-me-not are perennial rosettes with partially bracteate inflorescences and white corollas with exserted stamens.
Ourisia vulcanica is a species of flowering plant in the family Plantaginaceae that is endemic to the North Island of New Zealand. Lucy Moore described O. vulcanica in 1961. Plants of this species of New Zealand foxglove are showy, perennial, rhizomatous herbs that can be hairy with non-glandular hairs or sometimes glabrous. They have crenate, ovate leaves. The flowers are usually in pairs in each node, with an irregular calyx, and a white irregular corolla. The calyx and floral bracts have non-glandular hairs. The corolla tube is yellow with three lines of hairs and a ring of hairs inside. It is only found in the Volcanic Plateau area and is listed as At Risk - Naturally Uncommon.
Trithuria australis is a species of aquatic plant in the family Hydatellaceae endemic to Western Australia.
Trithuria bibracteata is a species of aquatic plant in the family Hydatellaceae endemic to Western Australia.
Trithuria filamentosa is a species of aquatic plant in the family Hydatellaceae endemic to Tasmania, Australia.
Trithuria fitzgeraldii is a species of aquatic plant in the family Hydatellaceae endemic to Western Australia.
Trithuria lanterna is a species of plant in the family Hydatellaceae endemic to Australia.
Trithuria polybracteata is a species of plant in the family Hydatellaceae endemic to Western Australia.
Trithuria submersa is a species of plant in the family Hydatellaceae endemic to the Australian states New South Wales, South Australia, Tasmania, Victoria, and Western Australia.
