Cyanothamnus rigens

Cyanothamnus rigenss, commonly known as the stiff boronia,[2] is a plant in the citrus family Rutaceae and is endemic to south-eastern New South Wales in Australia. It is a low, compact shrub with mostly trifoliate, glandular leaves and white to pale pink, four-petalled flowers in the leaf axils.

Stiff boronia
Cyanothamnus rigens in Morton National Park
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Rutaceae
Genus: Cyanothamnus
Species:
C. rigens
Binomial name
Cyanothamnus rigens
(Cheel) Duretto & Heslewood[1]
Occurrence data from Australasian Virtual Herbarium

Description

Cyanothamnus rigens is a compact shrub that grows to a height of 20–40 cm (8–20 in) with more or less hairy younger stems. The leaves are trifoliate with a petiole 1–4 mm (0.04–0.2 in) long. The leaflets are thick, often warty, narrow elliptic, 3–6 mm (0.1–0.2 in) long and 1–2 mm (0.04–0.08 in) wide. The flowers are white to pale pink and are arranged singly in leaf axils on a pedicel 1–3 mm (0.04–0.1 in) long. The four sepals are triangular to broadly egg-shaped, 1–3 mm (0.04–0.1 in) long, 0.5–1.5 mm (0.02–0.06 in) wide and hairy. The four petals are 2.5–3.5 mm (0.098–0.14 in) long and 1–2.5 mm (0.04–0.1 in) wide. The eight stamens alternate in length with those near the sepals slightly longer than those near the petals. The stigma is about the same width as the style. Flowering occurs from July to August and the fruit is a mostly glabrous capsule 2.5–3.5 mm (0.098–0.14 in) long and 1.5–2 mm (0.06–0.08 in) wide.[2][3]

Taxonomy and naming

The stiff boronia was first formally described in 1863 by George Bentham who gave it the name Boronia polygalifolia var. robusta and published the name in Flora Australiensis.[4][5] In 1929 Edwin Cheel gave it the name Boronia rigens and published the description in Journal and Proceedings of the Royal Society of New South Wales.[6][7] In a 2013 paper in the journal Taxon, Marco Duretto and others changed the name to Cyanothamnus rigens on the basis of cladistic analysis.[8] The specific epithet (rigens) possibly refers to the habit of this species compared to that of B. polygalifolia and B. nana.[3]

Distribution and habitat

Cyanothamnus rigens grows in heath and forest, sometimes on stabilised dunes between Bombala and Mt Coricudgy east of Rylstone.[2]

References
  1. "Cyanothamnus rigens". Plants of the World Online. Retrieved 22 September 2021.
  2. "Boronia rigens". Royal Botanic Garden Sydney. Retrieved 13 February 2019.
  3. Neish, Peter G.; Duretto, Marco F. (2000). "The taxonomy of Boronia anemonifolia and B. rigens (Boronia sect. Cyanothamnus, Rutaceae)". Muelleria. 14: 13–15. Retrieved 22 September 2021.
  4. "Boronia polygalifolia var. robusta". APNI. Retrieved 13 February 2019.
  5. Bentham, George; von Mueller, Ferdinand (1863). Flora Australiensis (Volume 1). London: Lovell Reeve and Co. p. 321. Retrieved 13 February 2019.
  6. "Boronia rigens". APNI. Retrieved 13 February 2019.
  7. Cheel, Edwin (1929). "Further notes on the genus Boronia". Journal and Proceedings of the Royal Society of New South Wales. 62: 297–298. Retrieved 13 February 2019.
  8. Duretto, Marco F.; Heslewood, Margaret M.; Bayly, Michael J. (2020). "Boronia (Rutaceae) is polyphyletic: Reinstating Cyanothamnus and the problems associated with inappropriately defined outgroups". Taxon. 69 (3): 481–499. doi:10.1002/tax.12242.
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