The Macrostelia Page

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Introduction

flower of Macrostelia grandiflora ssp. macilwraithensisMacrostelia is a genus of Malvaceous shrubs. Little information is readily available, but what I have found is presented here.

There are 4 described species, 3 from Madagascar, and 1 from northern Queensland. Another species has been discovered in northern Queensland, but has not yet been formally described.

Classification

The genus was erected by Hochr. for Macrostelia calyculata Hochr. and Macrostelia involucrata Hochr. of Madagascar. To this Hochr. and Humbert later transferred Hibiscus laurinus Baill. The current membership of the genus was achieved when Fryxell described the Australian representative of the genus, Macrostelia grandifolia P.A. Fryxell. The undescribed species is known, pro tem, as Macrostelia sp. Bolt Head.

DNA sequence evidence5 shows that the Australian forms fall within Hibiscus section Bombicella. No DNA sequences are available for the Malagasy species.

comparison of flowers of Australian taxaMacrostelia grandifolia ssp grandifolia P.A. Fryxell
Macrostelia grandifolia ssp macilwraithensis P.A. Fryxell
Macrostelia sp. Bolt Head

Flowers of the 3 Australian taxa are shown together for comparison in the image to the right. From left to right, these are the flowers of Macrostelia sp. Bolt Head, Macrostelia grandifolia ssp. grandifolia and Macrostelia grandifolia ssp. macilwraithensis.

All 3 Australian taxa are endemic to the Cape York Peninsula of northern Queensland. M. grandifolia ssp. macilwraithensis P.A. Fryxell is found in the McIlwraith Range; the nominate subspecies of M. grandifolia in the Tozer Range, which is part of the Iron Range, and lies to the north of the McIlwraith Range; and the remaining species is found on Bolt Head, which lies yet further north.

flower of Macrostelia grandiflora ssp. macilwraithensisM. grandifolia ssp. macilwraithensis is a shrub or small tree reaching 10-20 ft. in height. The flowers are white. The epicalyx segments are non-overlapping, and are about half the length of the calyx.

M. grandifolia ssp. grandifolia is a shrub 1 m or more in height, found on exposed granite bluffs. The protandrous flowers are a pale pink colour. This colour varies as the flower matures. The epicalyx segments are overlapping, and the epicalyx is longer than the calyx.

Macrostelia sp. Bolt Head is also a shrub. It has deep-pink flowers with red-veining. The epicalyx segments are deeply bifurcated, producing an epicalyx of prongs surrounding but not obscuring the calyx. The pedicel, epicalyx, calyx, petiole and underside of the leaf are densely covered with stellate hairs.

Synonyms: Macrostelia grandifolia ssp. macilwraithensis is in commerce as Macrostelia sp. Rocky River. Macrostelia grandiflora is current as an erroneous spelling of Macrostelia grandifolia.

Images

  • photograph of Macrostelia grandifolia ssp macilwraithensis at ANBG
  • photographs of all 3 taxa at The Malvaceae Gallery
  • Macrostelia laurina (Baill.) Hochr. & Humbert

    A red-flowered species from north east coastal regions of Madagascar.

    Synonyms: Hibiscus laurinus Baill. is a synonym of Macrostelia laurina

    Images

  • photograph at Missouri Botanic Garden
  • Acknowledgements

    Photographs are © 2001 G. Keena, and are reproduced with permission.

    References

    1. Australian Plant Name Index
    2. International Plant Name Index
    3. Colleen Keena (personal communication)
    4. Lyn Craven (personal communication)
    5. B.E. Pfeil et al, Phylogeny of Hibiscus and the Tribe Hibisceae (Malvaceae) Using Chloroplast DNA Sequences of ndfH and the rpl16 Intron (2002)

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