Family: Asphodelaceae
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:
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An endemic Australian genus of 33 taxa, 7 in S.Aust. (D. J. Bedford
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Biology:
No text
Taxonomic notes:
Often placed in the Xanthorrhoeaceae by recent authors.
Key to Species:
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1. Spike longer than the scape, usually more than 1.5 times as long |
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X. semiplana 5. |
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3. Packing-bracts subulate |
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X. australis 1. |
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3. Packing-bracts shortly acute to triangular |
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X. thorntonii 6. |
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1. Spike shorter than the scape, usually less than half as long |
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4. Leaves quadrate-rhombic in section |
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X. quadrangulata 4. |
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4. Leaves more or less depressed-cuneate to concave above in section |
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5. Leaves 1.9-3.5 mm wide; inflorescence less than 140 cm long; bracts shortly acute to acute |
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X. minor 3. |
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5. Leaves 3.2-7 mm wide; inflorescence longer than 145 cm; bracts linear-triangular to subulate |
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X. caespitosa 2. |
Author:
Prepared by D. J. Bedford
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