Boronia Sm., Tracts

Duretto, Marco F., Heslewood, Margaret M. & Bayly, Michael J., 2023, A molecular phylogeny of Boronia (Rutaceae): placement of enigmatic taxa and a revised infrageneric classification, Australian Systematic Botany 36 (2), pp. 81-106 : 101

Boronia Sm., Tracts Nat . Hist. 288 (1798)

Type: Boronia pinnata Sm.

Perennial herbs, shrubs, rarely small trees; glabrous or with simple or stellate hairs. Leaves opposite, decussate, rarely in whorls of three (see series Boronella ), simple or imparipinnate or rarely bipinnate (see section Alatae ). Inflorescences axillary or terminal; flowers solitary or in cymes or pseudo-umbels or panicles, bisexual, 4-merous, rarely 5-merous ( B. scabra subsp. attenuata Paul G.Wilson ). Sepals free, open, imbricate or valvate, persistent or caducous. Petals free, imbricate or valvate, not obviously glandular; tip straight or with a subterminal apiculum on the abaxial surface; 1- or 3-veined at base; caducous or persistent. Stamens 8, rarely 4 of them caducous ( B. parviflora ); filaments usually inwardly curved, semiterete, glabrous or hairy, usually verrucose towards apex; anthers introrse, apiculate or not, connective usually inconspicuous or cream coloured, all or only antepetalous anthers fertile (see series Boronia and series Persistens ). Disc prominent, usually entire, rarely with antepetalous ( B. octandra ) or antesepalous ( B. tetrandra ) lobes. Carpels 4; ovaries free though united at apex on adaxial margin by the solitary style. Fruit of 1–4 basally connate follicles (cocci), dehiscing explosively ventrally with separating, elastic endocarp. Seed: sclerotesta smooth or minutely tuberculate, rarely prominently rugulose ( B. cymosa ), glossy or dull. (Adapted from Duretto et al. 2020).

An Australian (including Tasmania) and New Caledonian genus of 134 species classified into 10 sections, including 9 confined to Australia, and 1, section Boronella , to Grande Terre, New Caledonia. Two sections, Corynophyllae and Inornatae , are newly described, and a new combination at sectional level is made for section Ovatae . Novel infrasectional classifications are provided for sections Boronella , with two series, and Boronia , with four series. Sections Alatae , Imbricatae , Pedunculatae , apart from the addition of subspecies for B. denticulata Sm. ( Duretto 2019) , and Valvatae , apart from the addition of five species ( Barrett et al. 2015), remain as previously circumscribed by Duretto et al. (2013) and Bayly et al. (2015) and are not dealt with further here.