Cuscutaceae

This small, almost cosmopolitan family has its greatest diversity in North and South America. Cuscuta is the only genus. Specialised, twining parasites of other plants, they occur in south-western, central and eastern Australia, mostly in open forests, grasslands and heaths.

Characteristic features of the family Cuscutaceae in Australia include:

• small, twining, parasitic, yellowish herbs with leaves reduced to small scales, attached to the stems of their host plants by swollen pads on the stems (haustoria)
  
• flowers in clusters, with petals united into a bell-shaped or globular corolla
  
• stamens fused to fringed scales at the base of the corolla tube
  
• fruit a dry (or slightly fleshy) capsule

Description

Annual or perennial. Chlorophyll absent and the whole plant whitish, yellowish or brownish. Plants partially or totally parasitic on the stems of their host. Internal secretions not obvious. Plants glabrous. Leaves reduced to scales, alternate and spiral, cauline, sessile. Stipules absent. Leaf scales simple, symmetric, lanceolate or ovate, one-veined, with the midrib inconspicuous, herbaceous. All the flowers bisexual. Inflorescences axillary or intercalary, consisting of glomerules or cymes. Bracts and bracteoles absent. Pollination by insects. Flowers odourless; sessile or stalked. Perianth regular, of 2 dissimilar whorls. Calyx segments free or fused, with (3–) 4–5 sepals or lobes, ?valvate or ?open in bud;calyx cup-shaped, herbaceous. Corolla segments fused, with (3–) 4–5 petals or lobes, alternating with the sepals/calyx lobes, imbricate in bud, fused; corolla bell-shaped or urn-shaped, cream, without contrasting markings, membranous; claws absent; lobes ±entire. Fertile stamens 5, opposite to the sepals or calyx lobes, at least partly fused to the corolla, free of the ovary and style, distinct from each other, all ±equal. Anthers basifixed, not versatile, opening sideways or inwards by longitudinal slits, 2-celled. Ovary superior and sessile. Carpels 2, fused; ovary with 2 locules. Style terminal, branching from the base. Ovules 2 per locule, sessile; placentation basal or axile. Fruit a dry dehiscent capsule with irregular or circumscissile dehiscence; the perianth on the maturing fruit dry and persistent. Disseminule macro-surface featureless, dull, cream, yellow or brown. Seeds 1–4 per fruit. Aril absent. Cotyledons 0. Embryo curved or coiled.
(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 Cuscutaceae has not yet been published in the Flora of Australia. It will appear in Volume 30.

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

† = some species native, others introduced

†Cuscuta