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Stackhousiaceae


This family is almost entirely Australian, with only two species of Stackhousia occurring outside Australia (one in Malesia and Micronesia, the other in New Zealand). One or more species may be encountered almost anywhere in Australia, from alpine herbfields to the Central Australian deserts and the monsoonal tropics, always in open, grassy vegetation, usually on light-textured soils.

Characteristic features of the family Stackhousiaceae in Australia include:

  • annual or rhizomatous perennial, erect, prostrate or cushion-forming herbs, sometimes sub-shrubby, often with rather stiff, wiry stems and relatively small, sparse leaves
  • leaves alternate, usually narrowly obovate to linear, sometimes reduced to scales
  • flowers greenish, white or cream, usually in terminal racemes or spike-like inflorescences
  • sepals and petals 5, the latter free or united into a narrow tube
  • stamens 5
  • ovary superior but enclosed in a cup-shaped or tubular hypanthium (superficially appearing inferior), developing into a fruit of 3–5 small, dry nutlets

Description

Annual, biennial or perennial herbs, or rarely evergreen shrubs. Leaves rarely ±absent. Perennating by rhizomes, stolons or ?crowns. Vegetative reproduction absent or by ?stolons. Stem internodes terete, or distinctly angled, or winged. Internal secretions not obvious. Plants glabrous, or with simple, non-glandular, uniseriate or multiseriate hairs. Leaves on adult plant well developed, or rarely much reduced (i.e. to scales, etc), alternate and spiral, all or mostly cauline, sessile, or rarely petiolate or subsessile. Stipules apparently absent or present, free, bristle-like, falling off early or persistent. Lamina simple, symmetric, linear, subulate, ovate, lanceolate, elliptic, oblong, obovate or spathulate; base cuneate or attenuate; margins entire, ±flat; venation one veined, rarely pinnate, with the midrib conspicuous or inconspicuous, and the tertiary venation absent; not punctate; herbaceous, rarely succulent; distinctive odour absent. All the flowers bisexual. Inflorescences terminal or rarely axillary, consisting of spikes, racemes, panicles, heads or solitary flowers, or apparently umbels. Bracts present. Bracteoles absent or present. Pollination by insects. Flowers odourless or fragrant, sessile or stalked. Free hypanthium present or apparently absent. Floral disc absent or present; nectaries absent or present on the disc or ?the anthers. Perianth of 2 dissimilar whorls, imbricate in bud. Calyx regular; segments free or apparently fused, with 5 sepals or lobes; calyx cup-shaped, bell-shaped or tubular, herbaceous, leathery or succulent. Corolla regular, or rarely irregular; segments free or fused, with 5 petals or lobes, alternating with the sepals or calyx lobes; corolla salver-shaped, tubular, or rarely 2-lipped, white, cream, yellow, orange, rarely pink, blue, green or brown, without contrasting markings, membranous or succulent; claws absent or present; lobes ±entire. Fertile stamens 5, opposite to the sepals or calyx lobes, free from each other and from all other flower parts, ±equal, or unequal and then alternating long and short. Anthers basifixed; not versatile, opening inwards by longitudinal slits, 2-celled; appendages absent or apical. Ovary superior and stalked, or apparently inferior. Carpels 35, fused; ovary with 35 locules. Style terminal, single and branched above, with the stigma clavate. Ovules 1 per locule; placentation basal. Fruit dry, a schizocarp forming mericarps (cocci); the perianth on the maturing fruit deciduous. Disseminule macro-surface featureless or with straight or hooked hairs, bristles, spines or wings; micro-surface ±smooth, muricate, tuberculate, rugose or verrucose, yellow, green, brown, without contrasting markings, or conspicuously patterned, glossy or dull. Seeds 5 per fruit. Embryo straight.
(Note: this description has been generated from the coded data compiled for the key. Any errors in the key data will be reflected in the descriptions.)

A treatment of the family Stackhousiaceae has been published in:
Flora of Australia 22: 186-199.

Australian genera of Stackhousiaceae (as recognised for the Flora of Australia)

Macgregoria
Stackhousia
Tripterococcus


Macgregoria racemigera (flowering plant)
Photo: A.S.George A.S.George 


Stackhousia monogyna (flowers)
Photo: K.Thiele K.Thiele 


Stackhousia pubescens (flowers)
Photo: F.Humphreys ANBG 


Stackhousia pulvinaris (flowering plant)
Photo: C.Totterdell ANBG