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FNA | Family List | FNA Vol. 12 | Phyllanthaceae

14. Phyllanthus warnockii G. L. Webster, Contr. Univ. Michigan Herb. 25: 235. 2007.

Sand reverchonia Sand reverchonia

Reverchonia arenaria A. Gray, Proc. Amer. Acad. Arts 16: 107. 1880, not Phyllanthus arenarius Beille 1927

Herbs, annual, monoecious, 2–5 dm; branching not phyllanthoid. Stems terete, not winged, glabrous. Leaves spiral, all well developed; stipules not auriculate, reddish purple to pale brown; blade elliptic to narrowly oblong-elliptic or nearly linear, (15–)20–40(–45) × (1.8–)2.5–8(–9) mm, base cuneate-attenuate, apex acute to mucronate, both surfaces glabrous. Inflorescences cymules, borne on lateral branches only, bisexual, with 1 pistillate flower and 4–6 staminate flowers. Pedicels: staminate 1.5–2.5 mm, pistillate spreading to sharply recurved, (2.5–)3.2–6.5(–8.7) mm. Staminate flowers: sepals 4, dark reddish purple, central portion sometimes paler, medially incurved and distally spreading (calyx appearing urceolate), 1.5–2.5 mm; nectary intrastaminal, annular, 4-lobed; stamens 2, filaments distinct. Pistillate flowers: sepals (5–)6, dark reddish purple, central portion sometimes paler and greenish purple, proximally flat to incurved and distally spreading, (1.3–)1.5–2.5(–2.9) mm, 1-veined; nectary annular, entire or 6-angled. Capsules 7–9.8 mm diam., smooth. Seeds mottled light and dark brown, (4.4–)4.7–6.2(–6.6) mm, 2 surfaces minutely papillate, 1 surface smooth. 2n = 16.

Flowering and fruiting summer-fall. Dunes; 300–1800 m; Ariz., Colo., Kans., N.Mex., Okla., Tex., Utah; Mexico (Chihuahua).

Phyllanthus warnockii is endemic to quartz sand dunes. Although always recognized as close to Phyllanthus, it generally has been segregated as the monospecific Reverchonia because of its unique habit (leafy main stems and flowers restricted to lateral branches), calyx shape and color, staminate nectary, and embryo with linear cotyledons. Phylogenetic analysis of DNA sequence data shows that P. warnockii not only is embedded within Phyllanthus, but also that it is most closely related to P. abnormis, which also is restricted to sandy soil (H. Kathriarachchi et al. 2006). These results suggest that the peculiar habit of P. warnockii reflects partial loss of the phyllanthoid branching syndrome.


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