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Pleurandra juniperina Turcz., Bull. Soc. Imp. Naturalistes Moscou 22(3): 6. Type citation: "Nova Hollandia, Swan-River Drum. coll. III. n. 2." (holo: KW 1000422 image!; iso: K 687504 image!, MEL 666815!).
Map 1. Distribution of Hibbertia juniperina in southwestern Western Australia. Stars indicate anomalous specimens with less protuberant midribs, discussed under Notes.
Low, often dense (rarely diffuse), sometimes prostrate and cushion-like shrubs 0.1–0.3(–0.4) m high; young branchlets glabrous or with few, sparse, white, multi-armed hairs when very young, with obscure tufts of short hairs in the leaf axils. Leaves spreading, scattered, linear, (8–)10–15(–25) mm long, 0.6–1 mm wide, the margins revolute and tightly abutting the midrib, which is prominent and protuberant with respect to the margins, the abaxial surface obscured; adaxial surface usually finely and sparsely tuberculate, glabrescent but usually with sparse, hooked hairs until mature, rarely almost glabrous from a young age, with short, multi-armed hairs at the very base; abaxial midrib smooth except for prominent tubercles on the flanks where it meets the lamina, which is glabrous (but is almost or completely hidden within the lacunae formed between the margins and the midrib and usually requires dissection to reveal); petiole abaxially glabrous; apex tapering and pungent-pointed. Flowers pedicellate, from upper leaf nodes or on lateral shoots, the pedicels 5–15 mm long, glabrous or with sparse, minute, stellate hairs below the flower; bract 1, subtending the flower at the apex of the pedicel, ovate, 1.5–2 mm long, abaxially glabrous, adaxially and on the margins minutely pubescent. Sepals ovate-acute and usually apiculate, 3.2–5.2 mm long, herbaceous, glabrous (the inner sepals with minute stellate hairs where overlapped by the outer in bud); midribs absent (or, if present, not prominent); outer and inner sepals similar in size and shape but the inner slightly broader and scarious-margined. Petals 5, yellow, broadly obovate, 5.5–7(–8) mm long, deeply emarginate. Stamens 10(12), all on one side of the gynoecium and curving over it like a hand of bananas; filaments 0.4–0.5 mm long, fused at the base into a robust claw; anthers rectangular, 1.5–2 mm long, dehiscing by introrse, longitudinal slits. Staminodes 2 either side of the stamens, rarely also with a few behind the stamens. Carpels 2; ovaries globular, densely pubescent; styles inserted excentrically on the carpel apex, parallel and curved beneath the stamens, 1.2–1.6 mm long. Ovules 2 per carpel. Fruiting carpels and seeds not seen.
Selected specimens examined (all PERTH): between Gingin and Regans Ford (2862921); Boonanarring Nature Reserve (3040895, 6740839); Bullsbrook (2862883); Gingin (3040976, 3041301); Jurien Bay (5799856, 6969356); Lesueur National Park (4067517, 4442636); Midland (2435233); Moore River National Park (3825310, 5895855); Regans Ford (2863162); Wannamal (5684889, 8415412); Yandin Hill (5684781).
For full specimen details, see the following batch search of the ALA for the above set of specimens: https://biocache.ala.org.au/occurrence/search?q=qid%3A1695077085933&qualityProfile=ALA&disableQualityFilter=scientific-name#tab_mapView
Map 1. Distribution of Hibbertia juniperina in southwestern Western Australia. Stars indicate anomalous specimens with less protuberant midribs, discussed under Notes.
Diagnostic features. Differs from the other species segregated from H. acerosa in the abaxial leaf midrib being broad and prominent and usually protuberant above the level of the margins (cf. usually flush with or recessed below the level of the margins), and the bract subtending the flower being ovate rather than linear. The leaves in H. juniperina also tend to be rather brighter green and glossy on herbarium sheets, contrasting with duller, greyish-green leaves in the other taxa.
Phenology. Flowers between August and November, with a peak in September.
Distribution & habitat. Occurs in south-western Western Australia between the vicinity of Mount Lesueur and Chittering, in the northern Swan Coastal Plain and southern Geraldton Sandplains IBRA bioregions (Map 1), with an early collection from Midland Junction near Perth, in shrublands, heaths and woodlands usually dominated by Proteaceae, on lateritic and sandy to light loamy soils.
Conservation status. Common and widespread and not considered to be at risk.
Notes. Two specimens at the northern end of the range, from the Mount Lesueur area (PERTH 3041115 and 3042081), have somewhat finer, longer leaves, but match typical H. juniperina in other respects. In several specimens from the western edge of the range (e.g. PERTH 3040879, 3312348, 5717833) the midribs are not so prominently protuberant, thus being somewhat similar to some specimens of H. callida, but in other respects these match H. juniperina and are here included within it.
There are three duplicates of Drummond III, 2. The K sheet bears a specimen tag with "2/Pleurandra cognata Steud?/1845/Swan River/Drummond". Pleurandra cognata is a synonym of H. acerosa sens. str. The KW sheet bears a specimen tag with the number "2" and a sheet label with "Pleurandra juniperina/Nova Hollandia. Swan River/Drum. coll. III n. 2", while the MEL sheet bears the same specimen tag and a sheet label in Mueller's hand with "Hibbertia acerosa Benth./WA/2/J.Dr.". Based on the morphology, all three sheets may come from one gathering. The KW sheet is a holotype (Mosyakin et al., 2019).