Hibbertia acaulothrix Toelken APNI*
Description: Erect shrubs up to 1.1 m tall, with several stems; branches bluntly ridged to scarcely flanged from the leaf base; tomentose or pubescent with ± persistent, dense multiangulate fascicled hairs.
Leaves cuneately oblong-oblanceolate, 6−15 × 2−5 mm, flat, entire; upper surface distinctly grooved along the central vein; vestiture moderately dense with spreading to antrorse fascicled hairs (usually with 1–3 arms, or up to 5 on the margin) becoming tuberculate; lower surface with central vein broader and often raised above revolute margins, velutinous with erect to spreading multiangulate broad-based fascicled hairs (7−14 arms); apex usually truncate-emarginate, rarely rounded with recurved vein-end; base gradually constricted into indistinct petiole, 0–0.3 mm long. Leaves without axillary tufts of hairs. Slightly discolourous; juvenile leaves (coppicing growth) larger but similar to normal leaves, entire, with finer and larger hairs.
Flowers single, terminal, sessile or almost so, often on lateral shoots; penduncle ± absent; bracts linear-oblanceolate to linear-spathulate, 8−10 × c. 2 mm, usually longer than outer calyx, pointed, ridged, below pubescent to tomentose or velutinous, above tomentose. Calyx with lobes slightly unequal,linear-lanceolate to oblanceolate, 6−7 × c. 2.5 mm, scarcely longer than inner calyx, pointed to acute, ridged, outside stubble-like to velutinous along margins, inside puberulous to pubescent on the upper third and the margins; inner calyx lobes (2/3) oblongovate, (4.2–) 4.5−5.5 (–6.3) × 3.1−3.8 (–4.1) mm, acute to cuspidate, scarcely ridged, stubble-like to pubescent on a central band and with fascicled cilia on broad membranous margin, inside glabrous. Petals obovate, (7.4–) 7.8−9.5 (–10.2) × (4.3–) 5.0−7.0 (–8.8) mm long, scarcely bilobed. Stamens 9−13 (plus some staminodes), subequal except for 1 (–3) longer ones, in ± 5 bundles around the ovaries; filaments narrow throughout, 1.3−1.8 mm long, slightly connate basally; anthers narrowly obloid, rarely obloid-ovoid, 1.1−1.3 mm long, 1 (–3) longer ones (1.8−1.9 mm long) in the centre, abruptly constricted above and below. Pistils 2; ovaries obovoid, each with 2 (–4) ovules above one another, hirsute, style attached to dorsal apex of ovary then ± erect such that stigmas are lateral to the upper part of the longer± incurved anther(s).
Flowering: October – April.
Distribution and occurrence: found in few widely separated localities in New South Wales (CT, CC, SC). Conservation status. In Wadbilliga National Park “several thousand plants scattered over at least 3 ha.” were recorded by J.D.Briggs 2080.
On sedimentary rocks, recorded growing in Eucalyptus sieberi woodland or associated with Allocasuarina littoralis, Corymbia gummifera Leptospermum trinervium.
NSW subdivisions: CC, SC, NT, CT
Although the species is at present known only from a few well separated localities, the different populations show little variation. Leaves of young fastgrowing branches have usually predominantly simple hairs on the adaxial leaf surface and these and at least the larger hairs of the abaxial surface are more or less antrorse. Since a similar trend was found in both H. hermanniifolia and H. spathulata the absence of stalked fascicled hairs in this species is significant. The epithet “acaulo-thrix”, Greek, “stalklesshair” (noun in apposition) refers to the sessile hairs of this species in comparison to those of the very similar H. hermanniifolia.
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