Drosera |
Drosera rotundifolia |
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catch-fly, dew-threads, droséra, rossolis, sundew |
droséra à feuilles rondes, round-leaf sundew |
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Habit | Plants annual or perennial [rarely subshrubs], deciduous, stems 1–2 cm (except also caulescent stems to 8(–20) cm in D. intermedia), usually forming over-wintering buds (hibernaculae). | Plants forming winter hibernaculae, rosettes (2–)4–10(–15) cm diam.; stem base not bulbous-cormose. | ||||||||||||||||||||||||||||
Leaves | erect to prostrate; stipules adnate to petioles their entire length, 4–6 mm, margins fimbriate along distal 1/2; petiole differentiated from blade, 1.5–5 cm, glandular-pilose; blade suborbiculate, 0.4–1 cm × 5–12 mm, broader than long, much shorter than petiole. |
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Inflorescences | 2–15(–25)-flowered; scapes 5–35 cm, glabrous. |
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Flowers | 4–7 mm diam.; sepals connate basally, oblong, 4–5 × 1.5–2 mm, glabrous; petals white or pink, spatulate, 5–6 × 3 mm. |
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Capsules | obovoid, splitting between placentae. |
5 mm. |
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Seeds | 20–70, minute. |
light brown, fusiform, 1–1.5 mm, finely and regularly longitudinally striate, with metallic sheen. |
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On | both surfaces in strong sunlight, greener in shade (except D. tracyi, which lacks red pigment even in full sun), unlobed, suborbiculate, orbiculate, spatulate, or obovate, or cuneate to linear pink, or rose to pinkish lavender; stamens 5, usually connate basally; gynoecium 3-carpellate; styles 3, deeply bifid; stigma capitate. |
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x | = 10. |
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2n | = 20. |
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Drosera |
Drosera rotundifolia |
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Phenology | Flowering Jun–Sep. | |||||||||||||||||||||||||||||
Habitat | Sphagnum bogs, fens, beaver ponds, swamps, peaty gravels, sandy soil, wet sand (for example, disturbed bottoms of old sand pits, emergent sandy shorelines) in the North, lake and stream margins, sphagnous streamheads, and seeps in the South | |||||||||||||||||||||||||||||
Elevation | 0–3000 m (0–9800 ft) | |||||||||||||||||||||||||||||
Distribution |
Nearly worldwide |
AK; CA; CO; CT; DC; DE; GA; IA; ID; IL; IN; KY; MA; MD; ME; MI; MN; MS; MT; NC; ND; NH; NJ; NY; OH; OR; PA; RI; SC; TN; VA; VT; WA; WI; WV; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; SPM; Greenland; Eurasia; Pacific Islands (New Guinea)
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Discussion | Species ca. 170 (8 in the flora). Species of Drosera are concentrated in Latin America, South Africa, Madagascar, Australia, and New Zealand. Droseras, like all carnivorous plants, have leaves that attract, catch, digest, and absorb nutrients from small, mostly arthropod prey. They are characterized by gland-tipped multicelled hairs that move in response to stimuli and that catch and appress prey to the leaf blade, where sessile glands secrete enzymes that dissolve the soft tissues. The released nutrients enhance growth by supplementing those available from the poor soils where they grow. All species of Drosera are capable of moving their trichomes in response to contact with digestible prey. According to C. (1875), this movement can be induced by the mere touch of a part of a small insect with a single trichome. Besides having trichome movement, some species are able to curl their leaf blades to various degrees in order to maximize contact with prey. Some species of Drosera may act as annuals, especially if the habitats dry out. The plants can be locally abundant. In most species, the flowers open only in the mornings on sunny days, or not at all on overcast days, and fruits may form from self-pollination. Some species, notably D. intermedia, may exhibit vegetative proliferation, portions of the flowers developing into leaves or plantlets. Some species form over-wintering buds called hibernaculae, requiring a cold period to break dormancy. Some species of Drosera are reportedly utilized in herbal medicines to produce cough preparations and treat lung and skin ailments. F. E. Wynne (1944) showed that seeds of North American Drosera are diagnostic for each species. The following key is adapted from various sources, and the species are presented in alphabetic order. Natural hybrids are rare in Drosera, and usually are sterile. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Drosera rotundifolia was the carnivorous plant most studied by C. Darwin (1875). The species is circumboreal and is widespread across North America, much more common northward and rarer in the South. It is difficult to grow in warmer climates. M. L. Fernald (1950) recognized forma breviscapa (Regel) Domin, found in the Canadian Maritime Provinces, with scapes 1–4 cm long and 1–3 flowers, and var. comosa Fernald, found from Gaspé County, Quebec, to New England and northern New York, with the parts of the flowers modified to green gland-bearing leaves. Dwarf, few-leaved plants found in Alaska have been called var. gracilis Laested. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 6, p. 420. | FNA vol. 6, p. 424. | ||||||||||||||||||||||||||||
Parent taxa | Droseraceae | Droseraceae > Drosera | ||||||||||||||||||||||||||||
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Name authority | Linnaeus: Sp. Pl. 1: 281. (1753): Gen. Pl. ed. 5, 136. (1754) | Linnaeus: Sp. Pl. 1: 281. (1753) | ||||||||||||||||||||||||||||
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