Dodecahema |
Polygonaceae subfam. eriogonoideae |
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spineflower, spinyherb |
wild buckwheat |
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Habit | Herbs, annual; taproot slender. | Shrubs, subshrubs, or herbs, sometimes nearly arborescent (Eriogonum), perennial, biennial, or annual, homophyllous, polycarpic (rarely monocarpic in Eriogonum); taproot solid or, rarely, chambered (Eriogonum), slender to stout. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | arising directly from the root, spreading, solid, not fistulose or disarticulating into ringlike segments, sparsely glandular. |
prostrate or decumbent to spreading or erect, sometimes scapose, rarely absent (Eriogonum), without recurved spines, glabrous or pubescent, sometimes glandular; nodes not swollen; tendrils absent; caudex stems tightly compact to spreading and at or just below the soil surface or spreading to erect and above the soil surface, woody; aerial flowering stems decumbent to spreading or erect, arising at nodes of caudex branches, at distal nodes of aerial branches, or directly from the root, slender to stout and solid or slightly to distinctly fistulose, rarely disarticulating in ringlike segments (Eriogonum). |
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Leaves | usually quickly deciduous, basal, rosulate; petiole present; blade narrowly oblanceolate, margins entire. |
deciduous (persistent in some shrubby and matted Eriogonum species), basal or basal and cauline, rarely only cauline, rosulate, alternate, or infrequently opposite (Goodmania) or in whorls of 3 (Gilmania); stipules absent (possibly vestigial in some perennial species of Chorizanthe); petiole present, sometimes indistinct, not articulate or with extrafloral nectaries; blade simple, rarely lobed (Pterostegia), rarely awn-tipped (Goodmania). |
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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. |
terminal or terminal and axillary, cymose and dichotomously or trichotomously branched, or racemose, simple or compound umbellate, or capitate; bracts usually connate proximally, leaflike or scalelike, entire apically, sometimes awn-tipped, glabrous or pubescent. |
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Peduncles | spreading, peglike. |
absent or erect to deflexed relative to inflorescence branch, sometimes reflexed, straight or curved. |
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Involucres | 1 per node, tubular, cylindric, 6-angled; teeth 6, awn-tipped, awns uncinate. |
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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. |
(1–)2–30(–100) per involucral structure, occasionally with stipelike base distal to articulations (Eriogonum); perianth accrescent in fruit, mostly white to red, yellow, light green, greenish white, maroon, or purple, urceolate to campanulate, occasionally glandular or pustulose abaxially, nearly always minutely glandular along midvein adaxially, glabrous or pubescent; tepals (5–)6, in 2 whorls of 3, connate proximally, typically not forming tube (except Chorizanthe, Lastarriaea, Mucronea, Pterostegia), petaloid or, rarely, coriaceous (Lastarriaea), monomorphic or dimorphic, entire, emarginate, or lobed to laciniate apically, rarely awn-tipped (Lastarriaea) or apiculate (Eriogonum); nectary a disk at base of ovary; stamens 3, 6, or 9 (variously 3–9 in Chorizanthe, Mucronea); staminodes absent; filaments usually distinct, occasionally forming staminal tube (Chorizanthe); pistils 3-carpellate, homostylous; ovary 1-locular; ovule 1, orthotropous, placentation basal; styles 3, distinct; stigmas capitate. |
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Achenes | included, dark brown to black, not winged, 3-gonous, glabrous. |
brown to black or maroon, homocarpic, winged or unwinged, 3-gonous, less often lenticular or globose-lenticular to globose. |
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Seeds | embryo curved. |
embryo straight or curved. |
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Involucral | structures tubular (involucre) or consisting of a series of individual bractlike lobes (involucral bracts) arranged in whorls or spirals, rarely absent (Gilmania), awns present or absent; involucre cylindric, prismatic, turbinate, campanulate, urceolate, or funnelform with 3–8(–36) usually erect teeth or 4–12 spreading to reflexed lobes (teeth and lobes are distal portions of proximally connate involucral bracts); involucral bracts in 1–3 whorls, rarely in spirals (Johanneshowellia), free or connate only at base, linear to oblanceolate or ovate. |
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x | = ca. 17. |
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Dodecahema |
Polygonaceae subfam. eriogonoideae |
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Distribution |
CA |
Mainly temperate regions of w North America (Alaska to Mexico); uncommon in South America (Argentina and Chile) and e North America (WVa s to c Fla, e to Mo, Okla, and Tex) |
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Discussion | Species 1. 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. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Genera 20, species ca. 325 (19 genera, 281 species in the flora). Detailed habitat, elevation, and distribution data for the eriogonoid genera are maintained by the author and available on the Web at: “Eriogonoideae (Polygonaceae) of North America north of Mexico” (http://www.life.umd.edu/emeritus/reveal/pbio/eriog/key.html). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 474. | FNA vol. 5, p. 218. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | Centrostegia section Diplostegia | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | Reveal & Hardham: Phytologia 66: 86. (1989) | Arnott: in M. Napier, Encycl. Brit. ed. 7, 5: 126. (1832) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Web links |