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Electronic Flora of South Australia genus Fact Sheet

Family: Liliaceae
Xanthorrhoea

Citation: Smith, Trans. Linn. Soc. 4:219 (1798).

Derivation: Greek xanthos, yellow; rheo, I flow; alluding to the resin ("gum") that flows from the stem.

Synonymy: Not Applicable

Common name: Grass-trees, yaccas, blackboys.

Description:
Woody-stemmed perennials with an arborescent to subterranean item; stem branched or unbranched, covered with closely packed persistent leaf bases; leaves numerous in 1 or more terminal rosettes each of which forms a tuff or a crown of leaves; leaves long, linear, tapering from a broad thickened distinct leaf-base to a fine pointed more or less pungent tip; leaf transverse-sectional shape variable from quadrate-rhombic to broadly transverse-rhombic or narrow- to broad-cuneate; leaf margins bordered with fine more or less rigid hair-like structures.

inflorescence a short to very long cylindrical spike-like structure (here called the spike) of numerous closely packed sessile flowers, borne on a short or long, glabrous slender or thick and woody scape; the flowers in obscure clusters (condensed cymes) arranged spirally on the axis and subtended by prominent or obscure cluster-bracts, each flower surrounded by numerous bracts (here called packing-bracts); usually only 1 inflorescence per apex though 1 to few per plant; flowers hermaphrodite; perianth persistent, with 6 free segments in 2 whorls; the outer segments more or less chartaceous or scarious, erect, broadly linear to spathulate; the inner segments more or less soft and membranous, yellow, cream or white, broader and longer than the packing-bracts, the distal half recurved over the bract surface or conspicuously exserted at flowering, both whorls sometimes with a terminal more or less elongated narrow protrusion which always contains an adaxial tuft of hairs (here called a beak) and/or a hair-covered adaxial protrusion from the apex of the beak (here called the proboscis); filaments dorsiventrally flattened, with membranous margins which are broad at the base, tapering to a fine tip, glabrous, inserted on the receptacle or on the inner segments very close to the receptacle; anthers versatile, dorsifixed, dehiscing by slits; ovary superior, 3-celled, with several ovules per cell, tapering into the single terete style; stigma entire (sometimes grooved), terminal.

Fruits obtuse to long-pointed, straight or curved upwards, protruding from the persistent perianth and packingbracts, style base forming a hard point, loculicidally dehiscing, with 1 or 2 seeds per cell, 2-4 seeds usual per fruit; seeds dorsiventrally flattened, narrow-ovate to ovate, broad-triangular in median transverse section, semimatt, black.

Distribution:  An endemic Australian genus of 33 taxa, 7 in S.Aust. (D. J. Bedford

Biology: No text

Taxonomic notes: Often placed in the Xanthorrhoeaceae by recent authors.

Key to Species:
1. Spike longer than the scape, usually more than 1.5 times as long
 
2. Leaves 5-12 mm wide
X. semiplana 5.
2. Leaves 1-3 mm wide
 
3. Packing-bracts subulate
X. australis 1.
3. Packing-bracts shortly acute to triangular
X. thorntonii 6.
1. Spike shorter than the scape, usually less than half as long
 
4. Leaves quadrate-rhombic in section
X. quadrangulata 4.
4. Leaves more or less depressed-cuneate to concave above in section
 
5. Leaves 1.9-3.5 mm wide; inflorescence less than 140 cm long; bracts shortly acute to acute
X. minor 3.
5. Leaves 3.2-7 mm wide; inflorescence longer than 145 cm; bracts linear-triangular to subulate
X. caespitosa 2.

Author: Prepared by D. J. Bedford


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