can't open /Data/Synonyms.csv: error The Plagianthus Page

The Plagianthus Page

Malvaceae Info (Home)

Contents

  • Introduction
  • Classification
  • Lowland Ribbonwood
  • Saltmarsh Ribbonwood
  • Plagianthus Gallery
  • Synonymy of Plagianthus & Hoheria

  • Plagianthus regius (Poit.) Hochr.
    Plagianthus regius (Poit.) Hochr. subsp. chathamicus (Cockayne) de Lange
    Plagianthus divaricatus J.R. Forster & G. Forster
    Plagianthus ×cymosus T.Kirk

    Introduction

    Plagianthus is a genus with the family Malvaceae. The 2 species of Plagianthus are endemic to New Zealand (and the Chatham Islands). These are vernacularly known as ribbonwoods, a name which they share with species of the closely related (and fellow New Zealand endemic) genus Hoheria. Ribbonwoods are deciduous shrubs or trees, bearing small white or yellow-white flowers in late spring, followed by pendulous seeds.

    It is distinguished from Hoheria by the presence of smaller flowers with linear stigmas and solitary carpels. (Hoheria has clusters of 5 or more carpels.)

    Classification

    The genus name is a reference to the petals of a Plagianthus flower not being all the same size.

    The genus Plagianthus, as currently recognised, is endemic to New Zealand and the Chatham Islands, and consists of 2 species - the saltmarsh ribbonwood, Plagianthus divaricatus and the lowland ribbonwood, Plagianthus regius. It was introduced by J.R. and G. Forster for the former species. The latter species was first described by Poiteau, as Philippodendrum regium Poit., based on specimens raised from seed erroneously recorded as being collected from Nepal [1].

    In the past various authors have included species of Hoheria, and the Australian endemic genera Asterotrichion, Lawrencia and Gynatrix. Plagianthus linariifolia Buchanan is Coprosma rugosa Cheeseman, and belongs in Rubiaceae [2]. Plagianthus humilis Blanco is Munronia humilis (Blanco) Harms, and belongs to the Meliaceae.

    Plagianthus does not have the typical aspect of a mallow, either in habit or flower, and its familial placement was initially uncertain. Poiteau placed his Philippodendrum close to Dombeyaceae and Byttneriaceae (treated here as subfamilies Dombeyoideae and Byttnerioideae of family Malvaceae), and subsequent authors treated it as the type of family Philippodendraceae, subfamily Philippodendroideae or tribe Philippodendreae. Hooker placed Plagianthus divaricatus in Euphorbiaceae, but considered an alternative placement in Bombacaceae (treated here as subfamily Bombacoideae of family Malvaceae.

    The genus was subsequently recognised as belonging to the tribe Malveae, and as the titular member of the Plagianthus alliance, consisting of Plagianthus, Hoheria, Asterotrichion, Lawrencia and Gynatrix. Recent DNA sequencing has confirmed this grouping, and placed it, with the South American genus Sidasodes and two or three species of the polyphyletic genus Sida, as the sister group to the remainder of subtribe Abutilinae [3]. A case could be made for resurrecting subtribe Plagianthinae for this slightly expanded grouping.

    The two species hybridise where they come into contact, e.g. on the banks of tidal rivers, giving rise to Plagianthus ×cymosus T.Kirk.

    Plagianthus regius (Poit.) Hochr.
    Plagianthus regius (Poit.) Hochr. subsp. chathamicus (Cockayne) de Lange
    English (New Zealand) Lowland Ribbonwood, Manatu, Ribbonwood, Riverbank Ribbonwood

    Plagianthus regius is found over most of New Zealand, including Stewart Island and the Chatham Islands, but is absent from North Cape and Ninety Mile Beach in the far north. It grows in riparian habitats from sea level to 1500 ft, preferring moist soil.

    It has distinct seedling, juvenile and adult forms.

    The seedling form has an erect habit, and foliage similar to the adult form, but with truncate or cordate leaf bases.

    The juvenile form (except in subsp. chathamicus) is a dense bush of slender, interlaced, branches. The leaves are ovate, 5-15mm × 3-10mm, and serrated.

    In its adult form it is New Zealand's largest deciduous tree, reaching 50 ft in height. The adult form, in its earlier stages, is a graceful, small to medium tree, reminiscent in habit of a Silver Birch. (Hence, presumably, the synonym Plagianthus betulinus.) When older it becomes broader and bulkier. (A specimen growing in an open location in Christchurch has a spread of 15m, and a trunk with a diameter of 1m.)

    The foliage consists of ovate to ovate-lanceolate, toothed, leaves, from 1"-2½" long, and ¼"-2" wide, with a covering of stellate hairs on both surfaces. The yellowish-white flowers are small, but occur in large, tomentose, terminal panicles, in late spring. The calyx is campanulate. The petals are linear-oblong (narrower in male than in female flowers) and rounded at their tips. The staminal tube is long and slender, in the male flowers protuding beyond the petals, and bears many short-stalked anthers. The fruit is a small, ovoid, single-seeded, capsule, which on maturity splits down one side.

    The population on the Chatham Islands is classified as subsp. chathamicus. It is distinguished by a non-divaricating habit (i.e. non-interlaced branches) in the juvenile form.

    There are no known synonyms of Plagianthus regius.There are no known synonyms of Plagianthus regius ssp. chathamicus.

    Plagianthus divaricatus J.R. Forster & G. Forster
    English (New Zealand) Makaka, Runa, Saltmarsh Ribbonwood, Shore Ribbonwood, Swamp Ribbonwood

    A spreading deciduous bushy shrub, growing to 8ft in height, and 12ft in width, to be found in saltmarsh and swamp habitats, over the whole of New Zealand, including those regions of the far north from which Plagianthus regius is absent. Like Plagianthus regius it has distinct juvenile and adult forms.

    The juvenile form has 2-3.5cm long linear or spathulate leaves.

    The adult form has 0.5-2 cm long linear, spathulate or narrow obovate, dark green, leaves. It bears very fragrant, small, yellowish-white tubular flowers, with 8-12 stamens, borne, solitarily or in small clusters, in leaf axils, in late spring. The glabrous calyx is hemispherical in form. The fruit is a small, downy, capsule containing 1 or 2 seeds, on maturity bursting irregularly.

    There are no known synonyms of Plagianthus divaricatus.

    Plagianthus ×cymosus T.Kirk

    Plagianthus ×cymosus is a hybrid between Plagianthus divaricatus and Plagianthus regius. It commonly occurs along the banks of tidal rivers where its parents come into contact, but has been recorded in the absence of one or both parents.

    It is recorded from the valley of the McLennan River (Otago) [4], along the banks of the Pelorus River (Marlborough) [5], near Kaitaia in the Auckland Peninsula [6, 7], from the Miramar Peninsula [8], from the banks of Waihopai River (near Invercargill) [9, 7], the Chatham Islands [10], the vicinity of Dunedin [7] and the region of the Marlborough Sounds [7]. A record from the Bank's Peninsula [11] may have been a flowering plant of the juvenile form of Plagianthus regius [12].

    Cytology

    Both species of Plagianthus have diploid chromosome counts of 42, as does subsp. chathamicus.

    Images

    Phytophagous Insects

    Oleander Scale, Aspidiotus nerii Bouché, and Greedy Scale, Hemiberlesia rapax (Comstock) Ferris, are recorded on Plagianthus divaricatus in New Zealand.

    Pathogens

    The rust fungus Puccinia plagianthi McAlpine (aka Puccinia hoheriae) infects all species of Hoheria and Plagianthus [], and also the Australian species Gynatrix pulchella [] and Asterotrichion discolor. It causes leaf spotting and stem distortion, and can be diagnosed by the presence of irregular pale yellow, grey or brown blotches on both surfaces of green leaves or on distorted sections of the stem, by the presence of dark brown pustules (telia) (less than 2mm in diameter) on the lower surface of the leaves, either clustered in the blotches or scattered singly.on leaf surfaces, and by the presence of yellow spots (pycnia) on both surfaces of green leaves. Unlike many rust fungi Puccinia plagianthi does not (as far as is known) have an alternate host. It is not considered of economic importance, and control measures are not necessary. []

    References

    1. Poiteau, Description du Philippodendrum, nouveau genre de plantes, Annales des Sciences Naturelles 2, 8: 183-190 (1837)
    2. Peter J. de Lange, personal communication (2008)
    3. J.A. Tate et al, Phylogenetic Relationships Within the Tribe Malveae (Malvaceae, subfamily Malvoideae) as Inferred from ITS Sequence Data, Am. J. Bot. 92(4): 584-602 (2005)
    4. T.F. Cheeseman, Contributions to a Fuller Knowledge of the Flora of New Zealand. No. 7., Transactions and Proceedings of the Royal Society of New Zealand 52: 9-16 (1929)
    5. T.F. Cheeseman, Contributions to a Fuller Knowledge of the Flora of New Zealand: No. 1, Transactions and Proceedings of the Royal Society of New Zealand 39: 439-450 (1906)
    6. H. Carse, On the Flora of the Mangonui County, Transactions and Proceedings of the Royal Society of New Zealand 43: 194-224 (1910)
    7. L. Cockayne, Observations concerning evolution, derived from Ecological Studies in New Zealand, Transactions of the New Zealand Institute 44: 1-50 (1911)
    8. L. Cockayne & H.H. Allan, Notes on New Zealand Floristic Botany, including Descriptions of New Species, &c. (No. 5) , Transactions of the New Zealand Institute 57: 58-72 (1927)
    9. J. Crosby Smith, List of Phanerogamic Plan's Indigenous in the Southland District., Transactions of the New Zealand Institute 46: 220-246 (1914)
    10. L. Cockayne, Notes on New Zealand Floristic Botany, including Descriptions of New Species, &c. (No. 4)., Transactions and Proceedings of the Royal Society of New Zealand 56: 21-33 (1933)
    11. L. Cockayne, Some Hitherto-unrecorded Plant-habitats (III)., Transactions and Proceedings of the Royal Society of New Zealand 40: 304-315 (1907)
    12. R.M. Laing, The Vegetation of the Bank Peninsula, with a list of species (flowering plants and ferns), Transactions and Proceedings of the Royal Society of New Zealand 50: 161-191 (1919)
    13. International Plant Names Index
    14. The Hillier Manual of Trees and Shrubs, 6th edn (1991)
    15. RHS Gardeners Encyclopedia of Plants and Flowers (1989)
    16. NZERN
    17. W.J. Bean, Trees & Shrubs Hardy in the British Is.
    18. Joseph Dalton Hooker, Handbook of the New Zealand flora (1867)

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