Cuscuta polygonorum
Cuscuta
cuscute des renouées, smartweed dodder
coral-vine, dodder, dodder [aramaic and hebrew triradical root of verb k-s-, love-tangle
yellow-orange, slender to medium.
trailing or twining, attached to host by haustoria, greenish, white, yellow, orange, or pink-purple, filiform, glabrous.
sessile;
blade reduced, scalelike, 1–2 mm, surfaces glabrous.
dense, glomerulate;
bracts at base of clusters 1, at base of pedicels 0–1, ovate-triangular to lanceolate, membranous, margins entire, apex acute.
cymes or thyrses; pedicellate or not;
bracts 0–1(–11).
0–1 mm.
(3 or)4-merous, 2–2.7 mm, membranous, not papillate;
calyx brownish yellow, cupulate, equaling corolla tube length, divided 1/2–2/3 its length, not reticulate or shiny, lobes triangular-ovate, bases not overlapping, margins entire, midvein not carinate, without hornlike appendages, apex obtuse to rounded;
corolla white, drying yellow-brown, 1.8–2.5 mm, tube cupulate to shallowly campanulate, 1–1.4 mm, not saccate, lobes erect, triangular, equaling or longer than corolla tube length, margins entire, apex acute, inflexed;
infrastaminal scales usually well developed, sometimes poorly developed, oblong, 0.8–1.2 mm, shorter than to equaling corolla tube length, bridged at 0.1–0.2 mm, mostly shallowly 2-fid with 1–3 fimbriae on each side of filament attachment or irregularly fimbriate at apex, fimbriae (0.05–)0.1–0.3 mm;
stamens exserted, shorter than to ± equaling corolla lobes;
filaments 0.4–0.8 mm;
anthers 0.3–0.4 × 0.2–0.3 mm;
styles subulate, 0.4–0.9 mm, shorter than ovary.
(3 or)4 or 5-merous, thickened-fleshy to thin-membranous;
sepals ± connate, calyx usually campanulate, cupulate, or cylindric, rarely angled or slightly zygomorphic, 2–6 mm;
corolla usually white, white-cream, or yellowish, sometimes pink or purple, cupulate to cylindric, 2–6(–9) mm , limb (3 or)4- or 5-lobed;
infrastaminal scales usually present, dentate or fimbriate;
styles 1 or 2;
stigmas 2, ± globose or ± elongate.
capsular, depressed-globose to ovoid, indehiscent or dehiscence circumscissile.
depressed-globose, often appearing angled, 1.6–3 × 2.5–5 mm, not thickened or raised around relatively large interstylar aperture, not translucent, base ± enveloped by withered corolla, indehiscent.
3 or 4, obcompressed, subglobose or broadly ovoid to broadly ellipsoid, 1.4–1.6 × 1.2–1.3 mm, hilum region subterminal.
1–4, glabrous, seed coat honeycombed when dry and papillate when wet or seed coat epidermis cells rectangular and not honeycombed/papillate;
hilum terminal, subterminal, or lateral;
embryo uniformly slender, 1–3-coiled, rarely globose-enlarged at base;
cotyledons absent.
= 4.
Cuscuta polygonorum
Cuscuta
Species ca. 200 (51 in the flora).
Cuscuta is classified within Convolvulaceae; its outgroup relationships are not clear (S. Stefanović et al. 2002; Stefanović and R. G. Olmstead 2004). Pollen and gynoecium features suggest that Cuscuta is allied with Dicranostyloideae clade or Convolvuloideae Burnett (M. Welsh et al. 2010; M. A. R. Wright et al. 2011).
Some Cuscuta species parasitize numerous hosts; others have relatively narrow host ranges. Some of the former species can be weeds especially destructive to crops, including alfalfa, carrots, chickpeas, clover, cranberries, fava beans, flax, lespedeza, potatoes, tomatoes, and sugar beets. When growing on perennial hosts, haustoria of some Cuscuta species overwinter inside their hosts and generate new growth in spring (J. H. Dawson et al. 1994; M. Costea and F. J. Tardif 2006; K. Meulebrouck et al. 2009).
Seed dispersal has been considered unspecialized (J. Kuijt 1969); endozoochory by migratory birds was recently documented in some species (M. Costea et al. 2016). Worldwide dispersal of weedy Cuscuta species has been through contaminated seeds of forage legumes, especially alfalfa, clover, and lespedeza.
Identification of most Cuscuta species is usually a lengthy process: rehydration, dissection, and examination of flowers with a microscope may be necessary. For stem diameters, the following categories are used (T. G. Yuncker 1921): slender = 0.35–0.4 mm‚ medium = 0.4–0.6 mm, and coarse = greater than 0.6 mm. Measurements of floral parts were done on rehydrated mature flowers. Lengths of flowers were measured from base of calyx to tip of a straightened corolla lobe. Color of calyx and texture of calyx and corolla were noted only on dried flowers. Observation of papillae and multicellular appendages require magnifications of at least 50×. Orientation of corolla lobes (erect, spreading, reflexed) was noted in mature flowers. Dehiscence or indehiscence of capsules can be predicted early in development of ovaries; lines of dehiscence are readily detectable at the bases of young ovaries; the ovary wall will tear along the dehiscence line when light pressure is applied. Capsule walls sometimes rupture irregularly.
Three of the four subgenera recognized in Cuscuta are known from the flora area; members of subg. Pachystigma (Engelmann) Baker & C. H. Wright are endemic to South Africa (M. Costea et al. 2015).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Inflorescences thyrsoid: paniculiform, racemiform, or spiciform; styles usually 1, sometimes distally 2-fid or separating into 2; seed coat epidermis cells rectangular, not honeycombed when dry and papillate when wet. | subg. Monogynella |
1. Inflorescences monochasial cymes: corymbiform, fasciculate, glomerulate, paniculiform, racemiform, ropelike, spiciform, or umbelliform; styles 2; seed coat epidermis cells honeycombed when dry and papillate when wet. | → 2 |
2. Styles equal; stigmas clavate, cylindric, or terete. | subg. Cuscuta |
2. Styles unequal; stigmas globose. | subg. Grammica |
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