The Gynatrix Page

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Introduction

Gynatrix is a genus of dioecious Malvaceous shrubs. It has two species, both endemic to south east Australia.

Classification

The genus was introduced by Alefeld in 1862. The genus was considered monotypic until the second species was described in 1996. The name is a reference to the hairy ovary.

Gynatrix is related to the Australian endemic genera Asterotrichion and Lawrencia, and the New Zealand endemic genera Hoheria and Plagianthus, these genera collectively forming the Plagianthus alliancee grouping within the tribe Malveae and subfamily Malvoideae. On grounds of shared morphology I conjectured that Astertrichion was the most closely related genus. Subsequent DNA sequence studies [5] place the genus in a trichotomy with Asterotrichion and Plagianthus.

Gynatrix pulchella (Willd.) Alef.
Australian Flag Hemp Bush, Aboriginal Hemp

The distribution of Gynatrix pulchella is in New South Wales, the Australian Capital Territory, Victoria and Tasmania. It is rare in Tasmania. It grows in moist, semi-shaded, sites alongside water courses. It is naturalised in Chile.

G. pulchella is usually dioecious, i.e. bearing male and female flowers on different plants. It is an evergreen sclerophyllous shrub growing to 2-4m in height, and with a spread of 2m. The leaves are ovate with a heart-shaped based, from 2½"-4½" in length, and borne on a slender petiole half the length of the blade. They are green on both sides, and coarsely and irregularly toothed, often with two lateral lobes near the base. Young foliage is dotted with stellate hairs.

The flowers are cream to white. In common with other species in the Plagianthus alliance they lack an epicalyx. They have a campanulate calyx with 5 triangular lobes. The male flowers have 20 stamens, with the free filaments being a least one third of the length of the staminal column. The female flowers are smaller, with 20 sessile sterile anthers. The ovary has 5 carpels, each containing a single ovule. The style branches are thickened towards the top, and stigmatose for three quarters of their length.

The pollen grains are stephanoporate and subspheroidal, with widely spaced pores, and spines 3-5 microns high, 1-2 micros across at base.

G. pulchella is unusual amongst Malvaceous plants in being dioecious, and unusual amongst dioecious plants in that male plants allocate more resources to reproduction than female plants. [6]

In the British Is. Gynatrix is only hardy in mild districts.

The bark has been used as a source of fibre for the manufacture of rope; hence the vernacular names.

Propagation

Gynatrix can be propagated by seed or cuttings. Varying advice is given for treating the seed. It is said that it germinates readily from a spring sowing without any special treatment, but scarification, or treatment with hot water, smoke water or aerial smoke, may be recommended to improve the germination success rate. The current seasons growth is recommended as a souce of cutting material.

Pests

A fungal pathogen of Hoheria (Puccinia plagianthi) has also been reported from Gynatrix pulchella.

Images

  • photograph at Australian National Botanic Garden
  • photograph at Herring Island Park
  • Synonyms: Synonyms of Gynatrix pulchella include Abutilon pulchellum Sweet, Plagianthus pulchellus (Willd.) Hook.f., Napaea pulchellus Alefeld, Plagianthus pulchellus var. tomentosus Rodway, Plagianthus tasmannicus (Hook.) Benth, Sida pulchella Willd. and Sida tasmannica Hook.

    Gynatrix macrophylla N.G. Walsh
    Gippsland Hemp Bush

    A newly (1996) described species from eastern Victoria (Gippsland). No details are known to me, but it can be assumed that it has larger leaves that Gynatrix pulchella.

    References

    1. W.J. Bean, Trees & Shrubs Hardy in the British Is.
    2. Australian Plant Name Index
    3. International Plant Name Index
    4. K. Kubitzki and C. Bayer, The Families and Genera of Flowering Plants Vol. 5 (2003)
    5. Tate et al, Phylogenetic Relationships Within the Tribe Malveae (Malvaceae, subfamily Malvoideae) as Inferred from ITS Sequence Data, American Journal of Botany 92(4): 584–602 (2005)
    6. Leigh et al, Reproductive allocation in a gender dimorphic shrub: anomalous female investment in Gynatrix pulchella?, J. Ecology 94(6): 1261-1271 (2006)

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