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FNA | Family List | FNA Vol. 5 | Polygonaceae

16. Dodecahema Reveal & Hardham, Phytologia. 66: 86. 1989.

Spinyherb [Greek dodeka, twelve, and hema, dart or javelin, alluding to involucral awns]

James L. Reveal

Centrostegia A. Gray ex Bentham sect. Diplostegia Roberty & Vautier, Boissiera 10: 91. 1964

Herbs, annual; taproot slender. Stems arising directly from the root, spreading, solid, not fistulose or disarticulating into ringlike segments, sparsely glandular. Leaves usually quickly deciduous, basal, rosulate; petiole present; blade narrowly oblanceolate, margins entire. Inflorescences terminal, cymose, uniparous due to suppression of secondaries; branches dichotomous, not brittle or disarticulating into segments, round, sparsely glandular; bracts 3-4, positioned to side and opposite next distal subsequent branch or involucre, connate ca. 1/ 2 their length, lanceolate, awned, sparsely glandular. Peduncles spreading, peglike. Involucres 1 per node, tubular, cylindric, 6-angled; teeth 6, awn-tipped, awns uncinate. Flowers 3 per involucre; perianth white to pink, campanulate when open, cylindric when closed, pubescent abaxially; tepals 6, connate proximally, monomorphic, entire apically; stamens 9; filaments free, glabrous; anthers red to maroon, oblong. Achenes included, dark brown to black, not winged, 3-gonous, glabrous. Seeds: embryo curved. x = ca. 17.

Species 1: California.

Each of the 12 awns on each involucre of Dodecahema leptoceras is long and slender. They are more like those seen in Sidotheca (Eriogonineae) than those of any member of the Chorizanthineae. J. L. Reveal and C. B. Hardham (1989) reported a consistent chromosome count of n = 15 plus (seemingly) additional chromosome fragments that bring the number to approximately n = 17. More work is required to resolve the exact chromosome number for the species. A specimen (Meiere s.n., 4 May 1917, CAS) supposedly from Needles, San Bernardino County, is discounted.

Lower Taxon


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