Drosera
Drosera tracyi
catch-fly, dew-threads, droséra, rossolis, sundew
Tracy's or Gulf Coast threadleaf sundew, Tracy's sundew
erect;
stipules adnate to petioles their entire length, 10 mm, margins fimbriate, forming woolly appearance of cormose base;
petiole not differentiated from blade;
blade filiform, 30–50 cm × 1–2 mm, glandular trichomes pale green, drying pale greenish brown.
4–12(–24)-flowered;
scapes 25–60 cm, glabrous.
glandular-pilose.
15–30 mm diam.;
sepals connate basally, oblong to elliptic, 4–7 × 2–3 mm, glandular-pilose;
petals rose, (rarely white), broadly ovate, 12–17(–20) × 15 mm, apical margins erose.
obovoid, splitting between placentae.
5–6 mm.
20–70, minute.
black, ellipsoid, abruptly caudate-truncate at both ends, 0.5–0.8 mm, coarsely crateriform, pits in 16–20 lines.
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.
= 10.
= 20.
Drosera
Drosera tracyi
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 tracyi occurs on the Gulf Coastal Plain from southwestern Georgia to southeastern Louisiana. The species has been reported from South Carolina; no specimens from there have been seen. The leaves and flowers are larger than those of D. filiformis. An anthocyanin-free form with white flowers is known.
B. A. Sorrie (1998b) gave evidence from morphology and ecology that Drosera tracyi is distinct from D. filiformis. Drosera filiformis has been found growing with D. tracyi in Bay and Washington counties, Florida, without apparent hybrids (Sorrie). This seems to be a natural disjunction, but D. filiformis has been planted outside its range. An artificial hybrid, which is sterile, between these two species has resulted in a cultivar named ‘California Sunset.’
Many artificial hybrids have been made and given formal or informal cultivar names. The following sterile wild hybrids have been reported.
Drosera ×beleziana Camus (D. intermedia × D. rotundifolia): Nova Scotia, Michigan.
Drosera ×hybrida Macfarlane (D. filiformis × D. intermedia): New Jersey.
Drosera ×linglica Kusakabe ex Gauthier & Gervais (D. linearis × D. anglica): Quebec.
Drosera ×obovata Mertens & Koch (D. anglica × D. rotundifolia): British Columbia, southeastern Canada, Newfoundland, Quebec, Great Lakes region, northern California, Oregon, Washington, and New England.
Drosera ×woodii Gauthier & Gervais (D. linearis × D. rotundifolia): Quebec.
Drosera capillaris × D. intermedia, no hybrid name given: Pender County, North Carolina.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blades filiform, not differentiated from petioles; stem base bulbose-cormose (from expanded petiole base); petals 7–17(–20) mm | → 2 |
1. Leaf blades linear or suborbiculate to obovate, elongate-spatulate, or cuneate, usually differentiated from petioles; stem base not bulbose-cormose; petals 3–7(–8) mm | → 3 |
2. Petals 7–10(–12) mm; leaf blades 8–25(–30) cm × 1 mm, glandular trichomes red to reddish purple, drying dark brown; scapes 6–26 cm. | D. filiformis |
2. Petals 12–17(–20) mm; leaf blades 30–50 cm × 1–2 mm, glandular trichomes pale green, drying pale greenish brown; scapes 25–60 cm. | D. tracyi |
3. Scapes stipitate-glandular; stipules absent or reduced to minute hairs; seeds black, crateriform. | D. brevifolia |
3. Scapes glabrous; stipules present; seeds reddish brown, light brown, brown, or black, striate, areolate, papillose, crateriform, or ridged | → 4 |
4. Leaf blades suborbiculate, (broader than long); seeds finely longitudinally striate. | D. rotundifolia |
4. Leaf blades linear, orbiculate, or spatulate to obovate or elongate-spatulate (longer than broad); seeds areolate, crateriform, or papillose | → 5 |
5. Stipules adnate to petioles | → 6 |
5. Stipules free from petioles or essentially so | → 7 |
6. Leaf blades obovate to elongate-spatulate; seeds fusiform, striate-areolate, 1–1.5 mm. | D. anglica |
6. Leaf blades linear; seeds rhomboidal or oblong-obovoid, crateriform, 0.5–0.8 mm. | D. linearis |
7. Plants always rosulate; petioles flat, sparsely glandular-pilose; petals usually pink, 6–7 mm; seeds coarsely papillose-corrugated, 0.4–0.5 mm. | D. capillaris |
7. Plants rosulate when young, developing leafy stems 1–8(–20) cm; petioles filiform, glabrous; petals white, 3–6 mm; seeds uniformly papillose, 0.7–1 mm. | D. intermedia |
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