Radyera Notes

Radyera farragei (F. Muell.) Fryx. & Hashimi
Radyera urens (L. f.) Bullock

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Introduction

Radyera is a genus of Malvaceous shrubs, distantly related to Hibiscus, with two species, one from Australia and one from South Africa.

Plants of the genus are soft-wooded subshrubs, with cordate, usually reniform, often lobed, leaves with serrate or crenate margins. They sometimes possess stipular nectaries. The flowers are borne in sparse cymes. They are involulcellate, the epicalyx being composed of from 8 to 10 fused bracteoles. The calyx is composed of 5 spreading lobes (fused at the base). The staminal tube is narrow, shorter than the petals, and antheriferous in its upper half. The pollen is oblate and zonocolporate. The style is undivided, with a capitate, 5-lobed stigma. The ovary is composed of 5 locules, each of which contains a few ovules. The fruit is a globose, 5-locular, capsule which is dehiscent first loculicidally and finally also septicidally, and is enclosed by the persistent calyx. The seeds are glabrous, black, ellipsoid in sharp, and posses an abundant endosperm, and a straight embryo. The diploid chromosome count is 32.

Classification

The genus was introduced by Bullock in 1956, with Radyera urens as the type species. Fryxell and Hashimi, transferred the second species, Radyera farragei in 1971. The genus has been considered related to Hibiscus, or even included therein. Recent opinion places it outside the Hibiscus tribe (Hibisceae) and the wider clade incorporating Malveae, Gossypieae, Hibisceae and Alyogyne. [4]

Radyera farragei (F. Muell.) Fryx. & Hashmi
English (Australian) Knobby Hibiscus, Desert Rose Mallow, River Hibiscus
German Knorriger Hibiscus

The Knobby Hibiscus is found in bush regions of the southern half of mainland Australia. It is threatened in Victoria, and absent from Tasmania and Queensland. It grows in intermittently wet areas, reaching 2m in height, before dying down, after seeding, until the next rain.

The whole plant is densely covered by stellate, white or gold, hairs. The leaves are relatively large, green on top, and white beneath, with a bristly texture.

The flowers are large, deep-lilac in colour, with a darker centre. The style is undivided, ending in a 5-lobed stigma. The calyx is toothed. The epicalyx is half the length of the calyx, and has a dissected form. The fruit is an egg-shaped capsule.

Seed of Radyera farragei is available commercially.

Radyera urens L. f. (Bullock)
Gernan Pomponmalve, Wildpompon
Afrikaans Wildepampoen

A South African species with brownish orange-red ("brick red") flowers.

Seed of Radyera urens is available commercially.

Synonyms: Hibiscus farragei F. Muell. is a synonym of Radyera farragei. Hibiscus urens L. f. is a synonym of Radyera urens.

References

  1. Australian Plant Name Index
  2. International Plant Name Index
  3. Kubitzki & Bayer, Malvaceae, in Kubitzki & Bayer, ed., Fam. Gen. Vascular Plants V: 225-311 (2003)
  4. Baum et al, Phylogenetic Relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as Inferred From Plastid DNA Sequences, American Journal of Botany 91(11): 1863–1871 (2004)

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© 2002, 2005 Stewart Robert Hinsley