Stylism
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Stylisma pickeringii |
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The Stylisma are a plant genus of the family of wind plants (Convolvulaceae). It consists of six species that are found exclusively in the temperate areas of North America .
description
Vegetative characteristics
Stylisma are perennial, prostrate or climbing climbing plants that usually grow herbaceous or rarely as subshrubs . They sprout annually from the base of the previous year's stems and crowns or from subterranean, branched trunks. The roots are thin, do not form tubers and are only slightly thickened at their origin, they penetrate deep into the ground. The stems have a circular cross-section and are very thin to densely tomentose with two-armed, adjacent trichomes , these are light green, light brown, gray or silver in color.
The leaves are short stalked or sessile. The leaf blade is entire and the shape is narrow elliptical, narrow elongated, elongated-elliptical, narrow linear-lanceolate, linear or modified from these forms. The base is blunt, pointed, tapered or slightly heart-shaped. The tip is pointed, blunt, slightly tapered or blunt-pointed. The leaf surface is hairless, covered with individual trichomes or lightly to densely tomentose. The trichomes consist of a short stem cell and a two-armed cell at the top. They are close-fitting and can be very fine and soft to long and firm, they are silver-gray, whitish or brownish in color.
Inflorescences and flowers
The inflorescences are in the armpits and are petiolate. They are either simple or compound dichasial (two-pronged) cymes from one to seven (occasionally up to twelve) flowers . The flower stalks are usually as long as the leaves, but they can also be longer. At the connection point between the inflorescence stalk and the flower stalk, there are almost opposite two scaly or deciduous bracts that are the same or almost the same size.
The sepals are herbaceous or slightly leathery. Mostly they are free from each other, but can also be fused together at the base. Their shape is oval or broadly lanceolate, they are of the same length or almost the same length, their tip is pointed, tapered or blunt, the edge is ciliate or entire. The outside is hairless or tomentose with attached trichomes. The crown is funnel-shaped or bell-shaped with a short corolla tube, the edge is entire or only slightly lobed. Usually the crown is colored white, but occasionally it is also lavender, red or pink. Along the middle of the petals, these are coarse-haired from the outside, the trichomes are two-armed, with one longer arm pointing towards the tips of the petals and the shorter arm occasionally not being visible. In the bud the crown is folded.
The stamens are not or only partially beyond the crown. The stamens are straight, unequal or almost equally long, flattened on the dorsiventral side and widened towards the base. Usually they are shorter than the stylus . The base of the stamens is often tomentose, but occasionally quite hairless. The anthers are mostly fixed on the back, occasionally they also seem to be fixed to the base, they open through longitudinal slits. The ovary is two-leaved and two-chambered, wire-haired or tomentose with two-armed trichomes, with both arms pointing to the opening of the crown. The ovary is surrounded by a basal flower base . There are two in each ovary specialist ovules . The styles are almost free or are partially fused together and do not or only partially protrude from the crown. The individual branches of the style are almost equally long or unequal in length, the style base can be clearly pronounced or hardly present and is often present on the fruit as a constant beak. The scars are depressed, head-shaped, rarely shield-shaped and almost spherical.
Fruits and seeds
The constant sepals are on the capsule fruits . The capsule is flabby and thin-walled, it contains one to four seeds . These are brownish, smooth, oval or roughly triangular and then rounded at the base. Often they are surrounded by a thin membrane, which has a reduced Arillus represents. The cotyledons are thin, narrow, strongly split in two and folded twice towards the radicle.
Occurrence and locations
All species of the genus Stylisma occur exclusively in the temperate areas of North America . The distribution area extends from New Jersey , Illinois and Iowa in the north to Florida and Texas in the south.
The locations are coastal and inland plains, where the species grow in dry, sandy pine stands and bushes, in dune bushes, in oak-pine forests, in clearings or in the prairie. Occasionally they are also found in moderately humid forests and on river banks, less often on the edges of lakes and ponds.
Systematics
External system
Within the bindweed family, the genus Stylisma is classified in the tribe Cresseae . Also in this tribe is the closely related genus Bonamia , to which the Stylisma were counted by some early authors. Phylogenetic studies have shown that the genus Bonamia is not monophyletic and that two species that have so far belonged to this genus form a sister class to the Stylisma .
Internal system
Six species are distinguished within the genus, two of which are in turn divided into two subspecies or varieties:
- Stylisma abdita T. Myint : It occurs in Florida.
- Stylisma aquatica (Walt.) Raf. : It occurs from the southeastern United States to southeast Texas.
- Stylisma humistrata (Walt.) Chapm. : It occurs from the southeastern United States to eastern Texas.
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Stylisma patens T. Myint . With the subspecies both found in the southeastern United States:
- Stylisma patens subsp. patens
- Stylisma patens subsp. angustifolia (Nash) T. Myint
- Stylisma pickeringii (Torr. Ex MA Curtis) A. Gray . With the varieties:
- Stylisma pickeringii var. Pickeringii : It occurs from New Jersey to the southeastern United States.
- Stylisma pickeringii var. Pattersonii (Fern. & Schub.) T. Myint : It occurs from the central United States to northwestern Louisiana.
- Stylisma villosa (Nash) House : It occurs from southeast Texas to Florida.
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Individual evidence
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- ^ Saša Stefanović, Daniel Austin and Robert Olmstead: Classification of Convolvulaceae: A Phylogenetic Approach. In: Systematic Botany , Volume 28, Number 4, 2003. Pages 791-806. doi : 10.1043 / 02-45.1 (currently unavailable) ( online )
- ↑ a b c d e f g Rafaël Govaerts (Ed.): Stylisma. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved November 22, 2017.
literature
- Tin Myint: Revision of the Genus Stylisma (Convolvulaceae) . In: Brittonia , Volume 18, Number 2, Apr. – Jun. 1966, pp. 97-117.