Aconogonon |
Polygonaceae subfam. polygonoideae |
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fleeceflower |
knotweed |
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Habit | Herbs, perennial; roots woody. | Trees, shrubs, vines, or herbs, perennial or annual, homophyllous (heretophyllous in some species of Polygonum); root fibrous or a solid taproot, rarely tuberous. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | ascending to erect, glabrous or pubescent to pilose or tomentose. |
usually prostrate to erect, sometimes scandent, not scapose, rarely with recurved spines (some species of Persicaria), glabrous or pubescent, sometimes glandular; nodes usually swollen; branches free (adnate to stems distal to nodes and appearing to arise internodally in Polygonella); tendrils absent (except in Antigonon and Brunnichia). |
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Leaves | deciduous, mostly cauline, alternate, petiolate or sessile; ocrea persistent or deciduous, chartaceous; blade narrowly lanceolate to ovate, margins entire, sometimes irregularly undulate. |
deciduous (persistent in Coccoloba and sometimes more than 1 year in Antigonon and Polygonella), basal or basal and cauline, rarely cauline only, mostly alternate; ocrea present, persistent or deciduous, cylindric to funnelform, chartaceous, membranous, coriaceous, or, rarely, foliaceous or partly so; petiole present or absent, rarely articulate basally (Fagopyrum, Fallopia, Polygonella, Polygonum), rarely with extrafloral nectaries (Fallopia, Muehlenbeckia); blade simple with entire margins, rarely undulate or lobed. |
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Inflorescences | terminal, subterminal, or axillary, racemelike or paniclelike; peduncle present or essentially absent. |
terminal or terminal and axillary, spikelike, racemelike, paniclelike, cymelike, or, rarely, capitate, comprising simple or branched clusters of compound inflorescences; bracts absent; peduncle spreading to erect, sometimes absent; clusters of flowers subtended by connate bracteoles forming persistent membranous tube (ocreola), awnless. |
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Pedicels | present. |
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Flowers | bisexual, 1–5 per ocreate fascicle, base stipelike or not; perianth nonaccrescent, creamy or greenish to yellowish white or pink, rotate, glabrous; tepals 5, connate ca. 1/4 their length, petaloid, slightly to distinctly dimorphic, outer 2 smaller than inner 3; stamens 8; filaments distinct, free or adnate to perianth tube, glabrous; anthers yellow to pink or reddish purple, ovate to elliptic; styles 3, erect or spreading, distinct or connate proximally; stigmas capitate. |
usually bisexual, sometimes bisexual and unisexual on same plant, rarely unisexual only, 1–20+ per ocreate fascicle, often with stipelike base distal to articulation; perianth often accrescent in fruit, often greenish, white, pink, yellow, red, or purple, usually unwinged and unkeeled (winged or, sometimes, keeled in Fallopia, rarely keeled in Polygonum), campanulate or urceolate, sometimes membranous, indurate, or fleshy in fruit, rarely developing raised tubercles proximally (Rumex), glabrous or pubescent, sometimes glandular or glandular-punctate; tepals 2–6, usually in 2 whorls, distinct or connate proximally and forming tube, petaloid or sepaloid, monomorphic or dimorphic; nectary a disk at base of ovary or glands associated with bases of filaments; stamens usually (1–)6–9, staminodes rarely present; filaments distinct, or connate basally and sometimes forming staminal tube, free or adnate to perianth tube; pistils (2–)3(–4)-carpellate; ovary 1-locular (sometimes with vestigial partitions proximally); ovule 1, orthotropous or, rarely, anatropous, placentation basal or free-central; styles 1–3, erect to spreading or recurved, distinct or connate proximally; stigmas peltate, capitate, fimbriate, or penicillate. |
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Achenes | includedor exserted, yellowish or dark brown, unwinged, 3-gonous, glabrous. |
yellowish, brown, red, or black, homocarpic (sometimes heterocarpic in Polygonum), winged or unwinged, usually 2–3-gonous, sometimes discoid, biconvex, or spheroidal, rarely 4-gonous. |
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Seeds | embryo usually curved. |
embryo usually straight or curved, rarely folded. |
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x | = 8, 10, 11. |
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Aconogonon |
Polygonaceae subfam. polygonoideae |
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Distribution | w North America; Europe; Asia |
Mainly temperate regions of North America |
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Discussion | Species ca. 25 (3 in the flora). The orthography of and author citation for the genus name have been matters of confusion. Meisner published the taxon as Polygonum sect. Aconogonon. Reichenbach elevated it to generic rank and changed the orthography, apparently deliberately, to Aconogonum. Debate centers on whether Reichenbach’s name is new (Aconogonum Reichenbach) or should be treated as Meisner’s section name elevated to generic rank [Aconogonon (Meisner) Reichenbach]. Following established custom, we here use Aconogonon. Aconogonon often is treated as a section of Persicaria (L.-P. Ronse Decraene and J. R. Akeroyd 1988); pollen morphology, inflorescence type, and seed and stem anatomy have been used by some taxonomists for segregation at the generic level (K. Haraldson 1978; Hong S. P. 1991). Aconogonon campanulatum (Hooker f.) H. Hara is planted as an ornamental. C. L. Hitchcock and A. Cronquist (1973) reported it as escaping and probably established west of the Cascade Mountains, especially in Seattle, Washington. P. Zika (pers. comm.) searched numerous herbaria in the Pacific Northwest. He found no voucher indicating that A. campanulatum has escaped there, although it is cultivated occasionally in the Seattle area; it therefore is excluded here. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Genera 28, species ca. 850 (16 genera, 160 species in the flora). Morphological (K. Haraldson 1978; L.-P. Ronse Decraene and J. R. Akeroyd 1988; Ronse Decraene et al. 2000; Hong S. P. et al. 1998) and molecular (A. S. Lamb Frye and K. A. Kron 2003) data provide support for separation of Persicaria from Polygonum. Further studies are needed to elucidate the relationships of allied genera, particularly Aconogonon, Bistorta, and Koenigia with Persicaria, and Fallopia and Polygonella with Polygonum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 597. | FNA vol. 5, p. 479. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | Polygonum section A. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | unknown: Handb. Nat. Pfl.-Syst., 236. (1837) | Eaton: Bot. Dict. ed. 4, 30. (1836) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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