Polygonella americana
Polygonella
American jointweed, southern jointweed
jointweed, polygonelle, wireweed
erect, branched proximally and basally, glabrous.
erect, decumbent, or prostrate, glabrous or scabrous.
adnate to stems, appearing to arise internodally.
persistent;
ocrea margins not ciliate;
blade linear to spatulate, (4–)5–12(–19) × 0.5–0.9(–1.2) mm, base barely tapered, margins not hyaline, apex obtuse to acute, often erose, glabrous.
deciduous or, rarely, with leaves persisting more than 1 year, sometimes fugacious, cauline, alternate;
ocrea usually persistent, sometimes disintegrating with age and deciduous distally, chartaceous or coriaceous;
petiole apparently absent, articulate basally;
blade filiform to broadly obovate, margins entire.
(7–)18–30(–60) mm;
ocreola encircling rachis, only the base adnate to rachis, apex acuminate.
terminal, racemelike, pedunculate.
spreading in anthesis and fruit, 0.4–2.3 mm, usually much longer than subtending ocreola.
present.
bisexual;
outer tepals sharply reflexed early in anthesis and in fruit, white to pink, elliptic to ovate, 1.2–2.2 mm in anthesis, margins erose;
inner tepals loosely appressed in anthesis and fruit, white to pink, ovate to suborbiculate, 1.7–2.9 mm in anthesis, margins erose;
filaments dimorphic;
anthers yellow or pink;
styles and stigmas 0.5–1 mm in anthesis.
bisexual, or some or all functionally unisexual, 1 per ocreate fascicle, base stipelike;
perianth nonaccrescent, white, pink, red, greenish, or yellowish, campanulate, glabrous;
tepals 5, distinct, petaloid, dimorphic, in 2 whorls with 2 outer and 3 inner or 2 outer and 2 inner plus 1 transitional;
stamens 8, in 2 series with 5 outer and 3 inner;
filaments distinct, free, dilated proximally, dimorphic, inner 3 dilated more abruptly than outer 5, with toothed or horned shoulders, or monomorphic (in P. fimbriata and P. robusta), glabrous (pubescent basally in P. basiramia);
anthers white, yellow, orange, pink, or dark red, elliptic to ovate or round;
styles (2–)3, erect, distinct;
stigmas (2–)3, capitate.
included, reddish brown, 3(–4)-gonous, 2.5–4 × 1.3–2.3 mm, shiny, smooth.
included or exserted, yellow-brown, brown, or reddish brown, wingless or narrowly winged, (2–)3(–4)-gonous, glabrous.
embryo straight or slightly curved.
= 11.
= 36.
Polygonella americana
Polygonella
Species 11 (11 in flora).
Polygonella is distinct from other genera of Polygonaceae in having branches adnate to the stem and thus appearing to arise internodally. Palynological, anatomical, and morphological evidence suggests Polygonella is closely related to Polygonum sect. Duravia (L.-P. Ronse Decraene et al. 2004; Hong S. P. et al. 1998; P. O. Lewis 1991).
Within-population allozyme diversity is lower in the two most widespread species of the genus as compared to their narrowly endemic congeners (P. O. Lewis and D. J. Crawford 1995). High levels of selfing or depletion of diversity due to Pleistocene glaciation have been suggested as possible explanations for the lower allozyme diversity within populations of Polygonella americana and P. articulata.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Margins of inner tepal deeply fringed; filaments of stamens monomorphic | → 2 |
1. Margins of inner tepal entire to erose; filaments of stamens dimorphic | → 3 |
2. Margins of leaf blade not hyaline; stems scabrous or, sometimes, glabrous proximally | P. fimbriata |
2. Margins of leaf blade hyaline; stems glabrous or sparingly scabrous on angles distally | P. robusta |
3. Ocreae margins ciliate | → 4 |
3. Ocreae margins not ciliate | → 6 |
4. Ocreolae not encircling rachis of raceme, their sides and bases adnate to rachis; inflorescences 2-6(-8) mm; outer tepals 0.5-0.9 mm in anthesis | P. parksii |
4. Ocreolae encircling rachis of raceme, only their bases adnate to rachis; inflorescences 10-45 mm; outer tepals 0.7-1.5 mm in anthesis | → 5 |
5. Stems branched at or below ground level | P. basiramia |
5. Stems simple, sometimes branched distally, if present, well above ground | P. ciliata |
6. Leaf blades (3-)9-30 mm wide, oblanceolate to obovate or broadly spatulate | P. macrophylla |
6. Leaf blades 0.3-6(-8) mm wide, filiform to broadly spatulate | → 7 |
7. Styles and stigmas 0.4-1 mm in anthesis; plants perennial | → 8 |
7. Styles and stigmas ca. 0.1 mm or less in anthesis; plants annual or perennial | → 9 |
8. Stems erect; outer tepals sharply reflexed early in anthesis and in fruit | P. americana |
8. Stems prostrate; outer tepals loosely appressed in anthesis, sometimes spreading in fruit | P. myriophylla |
9. Plants perennial; margins of leaf blade hyaline at least along distal 1/ 2; outer tepals usually reflexed in fruit | P. polygama |
9. Plants annual; margins of leaf blade not hyaline; outer tepals loosely appressed to spreading in fruit | → 10 |
10. Pedicels 0.9-3 mm, longer than subtending ocreolae; leaf blades 0.4-1.2 mm wide | P. articulata |
10. Pedicles 0.1-0.3 mm, as long as subtending ocreolae; leaf blades 0.8-5(-8) mm wide | P. gracilis |
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