Cuscuta polygonorum
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Drawing of Cuscuta polygonorum |
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| Engelm. |
Cuscuta polygonorum is a plant from the genus silk ( Cuscuta ) in the family of wind plants (Convolvulaceae).
description
Cuscuta polygonorum is a parasitic , herbaceous plant . The stems are 0.2-0.4 mm thick and yellow-orange.
The dense, ball-shaped inflorescences consist of four to 18 sessile to almost sessile flowers . At the base of the inflorescence there is always a bract , at the base of the flowers there can also be a bract. The bracts are membranous, ovate-triangular to lanceolate, 0.3 to 1 mm long and 0.2 to 0.9 mm wide. The leaf margin is entire, towards the front they are pointed, petioles are absent or are up to 1 mm long.
The flowers are usually four-fold, rarely three-fold. They become 2 to 2.7 mm long and membranous. They are colored white and turn yellow-brown when drying. Papillae are not formed. Milk tubes are in the crown , as well as in the carpels or capsules . They stand individually, are round at ovoid. The calyx is yellow-brown, neither shiny nor reticulate. It is cup-shaped and about as long as the corolla tube. The sepals are free for 1/2 to 2/3 of the length, the sepals do not overlap at the base. They are triangular-ovoid, straight, not keeled, the edge is entire, they are pointed towards the front.
The stamens protrude beyond the crown, are shorter or almost as long as the corolla lobes. The anthers are ovate to broadly elliptical, 0.3 to 0.4 × 0.2 to 0.3 mm long. The stamens are 0.4 to 0.7 mm long. The pollen grains are mostly 21 to 24.5 (rarely 18 to 26) µm in size. Between the stamens there are scales that reach the base of the stamens. They are elongated, usually slightly bilobed with one to three fringes on each side of the stamens, or with some irregular fringes on top.
The two styles are evenly awl-shaped, 0.4 to 0.9 mm long and thus shorter than the ovary . The scars are head-shaped and spherical.
The fruits are non-popping to irregularly popping capsules . They are depressed spherical, often appear angled, are not translucent. They are 1.6 to 3 × 2.5 to 5 mm long and neither thickened nor raised around the large aperture surrounding the stylus. The faded crown surrounds the base of the capsule. Each capsule usually contains four seeds . These are indented on the back, almost round, broadly ovoid to broadly elliptical. They are 1.45 to 1.6 × 1.25 to 1.39 mm long. The cells of the seed coat are pitted / papillary or polyhedral and measure 20 to 30 µm in diameter. Epicuticular wax is usually present. The hilum scar is slightly raised, the hilum is almost terminal, is elliptical in shape and measures 0.45 to 0.6 × 0.3 to 0.35 mm.
Occurrence
Cuscuta polygonorum is native to the United States and Canada .
ecology
The species parasitizes mainly on bird knotweed ( Polygonum ), but occasionally also on jumping herbs ( Impatiens ), morning glory ( Ipomoea ), Wolfstrapp (Lycopus), Penthorum , pointed burdock ( Xanthium ) and other plants.
literature
- Mihai Costea, Guy L. Nesom and Saša Stefanović: Taxonomy of the Cuscuta pentagona complex (Convolvulacea) in North America . In: SIDA, Contributions to Botany , Volume 22, Issue 1, 2006. Pages 151-175.
