Stylidium is a genus of dicotyledonous plants that belong to the family Stylidiaceae. The genus name Stylidium is derived from the Greek στύλος or stylos, which refers to the distinctive reproductive structure that its flowers possess. Pollination is achieved through the use of the sensitive "trigger", which comprises the male and female reproductive organs fused into a floral column that snaps forward quickly in response to touch, harmlessly covering the insect in pollen. Most of the approximately 300 species are only found in Australia, making it the fifth largest genus in that country. Triggerplants are considered to be protocarnivorous or carnivorous because the glandular trichomes that cover the scape and flower can trap, kill, and digest small insects with protease enzymes produced by the plant. Recent research has raised questions as to the status of protocarnivory within Stylidium.
Stylidium repens, the matted triggerplant, is a dicotyledonous plant that belongs to the genus Stylidium. S. repens is endemic to Australia and is found primarily in southwest Western Australia. This species is a creeping or scrambling triggerplant, which can spread over large areas as a tangled mat of stems and aerial roots. The older stems are grey whereas younger stems appear red and have terminal rosettes of small leaves, five mm to one cm in length. When the rains come, new roots and a one to three flowers emerge from the terminal rosettes. This is the only species of triggerplant known to regularly flower twice a year—in autumn and late spring. Pollination, which is typically very specialized in this genus, is achieved with a variety of insects in this species.
Oreostylidium is a genus of flowering plants in the family Stylidiaceae with a single species, Oreostylidium subulatum, that is endemic to New Zealand. O. subulatum is a very small plant with small, white flowers. It has a complicated botanical history that has led to a few proposals to move Oreostylidium to the related genus Stylidium. The researchers cite molecular data and suspect that this species is an extreme example of floral paedomorphosis. This would not be an unprecedented move since the single species was initially described as Stylidium subulatum in 1864 and later moved to its own genus by Sven Berggren in 1878. It possesses the same kind of glandular trichomes underneath the flower that make Stylidium species carnivorous plants, but it has not yet been tested for the presence of digestive enzymes.
Andersonia is a subgenus of Stylidium that is characterized by a linear hypanthium, recurved mature capsule walls, an erect and persistent septum, and many seeds. This subgenus occurs in areas of tropical northern Australia and into Southeast Asia and was named in honour of William Anderson, the surgeon and naturalist who sailed with James Cook.
Stylidium fimbriatum is a dicotyledonous plant that belongs to the genus Stylidium. It is an erect annual plant that grows from 15 to 30 cm tall. Oblanceolate leaves, about 16 per plant, form a basal rosette around the compressed stems. The leaves are generally 5–20 mm long and 2–7 mm wide. This species generally has one or two scapes and cymose inflorescences that are 15–30 cm long. Flowers are pink with yellow highlights. S. fimbriatum's distribution is confined to the area around Bachsten Creek in the Kimberley region in Western Australia. Its typical habitat is herbfields that are seasonally wet.
Stylidium aceratum is a dicotyledonous plant that belongs to the genus Stylidium. It occurs within the south west region of Western Australia
Stylidium subg. Centridium is a subgenus of Stylidium that is characterized by a globose hypanthium, a stipitate brush-like stigma, and gynostemium mobility not produced by a sensitive hinged torosus but by the movement of a cunabulum. All species with the possible and doubtful exception of S. weeliwolli are annuals. This subgenus appears to be most closely related to the genus Levenhookia, which suggests an ancestral relationship. Centridium was first published by John Lindley in the 1839 publication, A Sketch of the Vegetation of the Swan River Colony. Lindley created this subgenus to distinguish species which did not fit into either of the two other subgenera that had existed at the time. He initially placed Stylidium calcaratum, the newly described Stylidium androsaceum, and Stylidium stipitatum into subgenus Centridium. His description of S. androsaceum turned out to be synonymous with S. calcaratum and S. stipitatum is a synonym of Levenhookia stipitata.
Stylidium ceratophorum is a dicotyledonous plant that belongs to the genus Stylidium. It is an annual plant that is endemic to the Kimberley region of Western Australia and northern parts of the Northern Territory. It attains a height of 12–30 cm with a basal rosette of small leaves. The leaves are petiolate, obovate, or lanceolate and are only 0.2–1 cm long. Solitary scapes are produced that bear golden yellow or orange flowers, 7–9 mm across. Its habitat has been reported as being sandy soils on creek margins in the presence of Stylidium rubriscapum and Stylidium diceratum or in river paperbark stands. S. ceratophorum appears similar to S. diceratum and may be confused with the species since they both have orange flowers. S. ceratophorum's corolla is twice as large as S. diceratum, though, as well as the deeply divided posterior corolla lobes of S. ceratophorum.
Stylidium diceratum is a dicotyledonous plant that belongs to the genus Stylidium. The specific epithet diceratum is Greek for "two horns", referring to the two appendages that are present on the bend of the gynostemium. It is an annual plant that grows from 15 to 35 cm tall. The longer leaves are lanceolate and the shorter ones are spathulate, forming a basal rosettes around the stem. The leaves are around 5–8 mm long and 0.2-2.5 mm wide. Inflorescences are around 6–15 cm long and produce flowers that are orange with dark orange and pink veins and bloom from June to August in their native range. S. diceratum is only known from the type location, which is at creek crossings on the road to Beverley Springs in the Kimberley region of Western Australia. Its habitat is recorded as being sandy soils on creek margins. It grows in the presence of S. ceratophorum, S. rubriscapum, Drosera caduca, D. paradoxa, Byblis liniflora, and Grevillea pteridifolia. S. diceratum is most closely related to S. longicornu, but it can be confused with S. ceratophorum, which also has an orange corolla but twice as large.
Stylidium edentatum is a dicotyledonous plant that belongs to the genus Stylidium. It is an annual plant that grows around 6 cm tall. The elliptical leaves form a basal rosettes around the stem. The leaves are around 0.3-0.8 mm long with recurved margins. Inflorescences are produced on solitary scapes and bear flowers that are white with rose-coloured markings at the base of the corolla lobes and two tooth-shaped throat appendages present. S. edentatum was a previously overlooked species that is related to and appears similar to S. calcaratum and S. ecorne. Allen Lowrie and Sherwin Carlquist described this species in 1989 and argued that if S. ecorne is considered distinct from S. calcaratum, then certainly S. edentatum warrants placement at the species level. It differs from S. calcaratum and S. ecorne by the long petioles on its recurved leaves, and the cuneate, obtuse, and unlobed posterior corolla lobes. They also have a distinctive lateral toothlike appendage at the base of each posterior corolla lobe. S. edentatum is endemic to southwestern Western Australia.
Stylidium longicornu is a dicotyledonous plant that belongs to the genus Stylidium. It is an annual plant that grows from 10 to 30 cm tall. The obovate to spathulate leaves form a basal rosettes around the stem. The leaves are around 4–6 mm long. Inflorescences are unbranched racemes and produce flowers that are violet with white at the base and bloom from June to August in their native range. S. longicornu is endemic to the Kimberley region in Western Australia. Its habitat is recorded as being sand flats near sandstone. It grows in the presence of S. lobuliflorum, Rhynchospora, and Leptocarpus.
Stylidium weeliwolli is a dicotyledonous plant that belongs to the genus Stylidium. It occurs in the North West of Western Australia
Stylidium subg. Forsteropsis, as circumscribed by Allen Lowrie and Kevin Kenneally, contains five species of triggerplants from south-western Australia that are characterized by their tightly appressed leaves arranged in a spiral around the stem. This subgenus was originally described by Otto Wilhelm Sonder in 1845 as the genus Forsteropsis.
Stylidium imbricatum, the tile-leaved triggerplant, is a dicotyledonous plant that belongs to the genus Stylidium. It is an herbaceous perennial that grows from 12–50 cm tall and has divided stems covered with tile-like leaves that are arranged in a spiral formation around the stem. The ovate-elliptic leaves are basifixed and held closely against the stems. The leaves are around 1.5-1.8 mm long and 0.6-0.8 mm wide. Terminal inflorescences are racemose or spike-like and produce flowers that are reddish violet with laterally-paired lobes and bloom from April to May in their native range. S. imbricatum is only known from south-western Western Australia in Stirling Range National Park and Porongurup National Park south-east to Cheynes Beach. Its habitat is recorded as being sandy or laterite soils in swampy areas, rocky slopes, or heathland. S. imbricatum is distinct within its subgenus because it possesses obovate sepals. Its conservation status has been assessed as secure.
Stylidium leeuwinense is a species that belongs to the genus Stylidium. The specific epithet leeuwinense refers to the Cape Leeuwin region in Western Australia where the type location for this species is. It is an herbaceous perennial that grows from 15–60 cm tall and has divided stems covered with tile-like leaves that are arranged in a spiral formation around the stem. The lanceolate leaves are basifixed and held closely against the stems. The leaves are around 2.5-3.5 mm long and 0.5-0.8 mm wide. Terminal inflorescences are racemose or spike-like and produce flowers that are reddish purple with laterally-paired lobes and bloom from February to May in their native range. S. leeuwinense is only known from south-western Western Australia along the coast from Augusta to Denmark. Its habitat is recorded as being black, peat-sand soils in swampy areas or heathland. S. leeuwinense, along with S. preissii, is distinct within its subgenus because it possesses leaves without an apical mucro. It differs from S. preissii by its spike-like racemes.
Stylidium marradongense is a species that belongs to the genus Stylidium. The specific epithet marradongense refers to the Marradong region in Western Australia where the species is located. It is an herbaceous perennial that grows from 15–50 cm tall and has divided stems covered with tile-like leaves that are arranged in a spiral formation around the stem. The lanceolate leaves are basifixed and held closely against the stems. The leaves are around 1.5-2.0 mm long and 0.5-0.8 mm wide. Terminal inflorescences are racemose or spike-like and produce flowers that are shades of pink or white with pink at the base of the lobes and bloom from September to November in their native range. S. marradongense is only known from south-western Western Australia from Mount Saddleback to Marradong. Its habitat is recorded as being sandy laterite soils in open Jarrah forest with other species such as Banksia grandis, Banksia sessilis, and Persoonia longifolia. S. marradongense is closely associated with S. preissii because they both lack throat appendages. It differs from S. preissii by its spike-like racemes, apical mucro, and conical, capitate stigmas.
Stylidium preissii, the lizard triggerplant, is a species that belongs to the genus Stylidium. It is an herbaceous perennial that grows from 5–18 cm tall and has divided stems covered with tile-like leaves that are arranged in a spiral formation around the stem. The broadly trullate leaves are basifixed and held closely against the stems. The leaves are around 1.9 mm long and 1.0 mm wide. Inflorescences are umbellate racemes and produce flowers that are white, pale pink, or dark pink and bloom from November to December in their native range. S. preissii is only known from south-western Western Australia from Bremer Bay to Israelite Bay with a few populations near Jandakot. Its habitat is recorded as being white sandy soils in open heathland. S. preissii is distinct within its subgenus because it possesses a strap-like gynostemium column with a dilated cunabulum.
Stylidium semaphorum is a species that belongs to the genus Stylidium. The specific epithet semaphorum is Greek for "sign-bearing" and refers to the flower shape, which appears to have to be positioned in a V-shape, a semaphore code for "attention". It is an herbaceous perennial that grows 5–18 cm tall and has divided stems covered with tile-like leaves that are arranged in a spiral formation around the stem. The narrowly ovate leaves are basifixed and held closely against the stems. The leaves are around 2.0–2.3 mm long and 0.5–0.7 mm wide. The terminal inflorescences are spike-like racemes and produce flowers that are pale pink or white and bloom from September to October in their native range. S. semaphorum is only known from its type location in south-western Western Australia. The only population recorded is within the bounds of a nature reserve. Because of its small population levels, the government has declared this species to be rare in the wild, which is similar to a status of threatened, vulnerable, or endangered. Its habitat is recorded as being laterite gravel soils on a hill summit in the company with Banksia sessilis. S. semaphorum is distinct within its subgenus because it possesses sepals with short brownish apical mucro.
Stylidium perplexum is a species of triggerplant that is endemic to south-west Western Australia. It is a tuberous species that has many stems and has been described as "somewhat shrubby" at 15–40 cm tall. The linear leaves can be 2 cm long and are arranged around the stem in a rosette at the stem apices. The 8–19 cm tall scapes bear 6 to 14 flowers that are white with purple accents and corolla lobes that are laterally paired and 4–6 mm long.
Stylidium affine is a species in the genus Stylidium that is endemic to Western Australia.
