Asclepias uncialis
Asclepias Uncialis
Asclepias Uncialis is a plant of the genus milkweed ( Asclepias ) from the subfamily of milkweed plants ( Asclepiadoideae ).
- 4.1 Literature
- 4.2 Notes and references
Features
Vegetative characteristics
Asclepias Uncialis is a small, perennial, upright -growing plant with a rhizome -like rootstock. The slender, herbaceous shoots are ascending or decumbent, and only 5 to 20 cm long. The rootstock grow more densely packed, very sparse fluffy hairy shoots, which are unbranched. The constantly compared to alternate irregularly arranged on the stems leaves are short to very short -stalked ( 1-5 mm long), and very different in shape along the drive. The lower leaf blades are ovate, the higher standing spreading change rather abruptly to a linear - lanceolate shape. The outer end is obtuse to acute, the base rounded to obtuse. They are 1-2 cm long, 2-7 mm wide and very finely hairy fluffy.
Inflorescence and flowers
The few-flowered inflorescences are terminal or near- terminal side of the uppermost nodes present and sessile, rarely short-stalked. The stalked flowers are comparatively small, the very slender flower stalks are hairy 1 to 1.5 cm long and fine fluffy. The sepals are ovate - lanceolate, about 2 mm long, sparsely hairy fluffy. The corolla is wheel-shaped and strongly recurved, purple - pink petals. The tip is about 4 mm long. The single-row, pale pink to yellowish corona is sessile. The tip of the ( staminal ) Nebenkrone are short - sack- shaped, about 1.5 mm long and flattened at the top. The shape is created by rolling the tip inward. At the " seam" of the bag-like structure, the edges of which are bent at right angle and extended to the triangular, tapering projections. The tip of the corona are slightly shorter than the Gynostegium. The secondary extension on the inside of the tip is at approximately at mid- height. The inside flat extension is inflated, ovoid and only slightly longer than the tip. The stylus head is about 1 mm long and 1.5 mm wide.
Fruit and seeds
The follicles stand upright on the U-bent stems; they are approximately 4 to 6 cm long. In most cases, only one fruit per stem rarely develops, even two fruits.
Similar Species
Asclepias Uncialis is closely related to Asclepias cutleri and Asclepias brachystephana; all species are very small and restricted to dry habitats.
Geographical distribution and ecology
The distribution area of Asclepias Uncialis extends across the U.S. states of Arizona, Colorado, Nevada, New Mexico, Oklahoma, Texas, Utah and Wyoming. It grows in dry, sandy or rocky soils in 1100-2150 m above sea level. They bloom during May and June. First flowering plants but has been collected already the end of March. The flowers remain open four to eight days. The strong floral scent is described as " the scent of roses " or " fragrant citrus ". They produce much nectar. The fruits ripen in 40 to 60 days after fertilization. Since from the rhizome -like root stock several times standing far apart shoots arise, even a limited vegetative propagation is considered possible.
Taxonomy and systematics
The taxon was described in 1880 by Edward Lee Greene for the first time. 1941 Bassett Maguire described the taxon Asclepias ruthiae; the Artepithet honors his wife Ruth Maguire. Robert Everard Woodson held in 1954 both taxa for valid types. In contrast, Eric Sundell Asclepias ruthiae reduced in 1994 to a mere variety of Asclepias Uncialis. John T. Kartesz and Kanchi Natarajan Gandhi raised in 1991 to the rank of Asclepias ruthiae again to the subspecies. The Plant List accepts both of these subspecies. As synonyms of the subspecies ruthiae Asclepias eastwoodiana Barneby and Asclepias sanjuanensis salvation, Porter & Welsh ( 1989) are considered.
- Asclepias Uncialis subsp. Uncialis: This subspecies is very small, the shoots are only 5 to 10 cm long. The leaves are lanceolate to linear. The fluffy hair is limited to the leaf margins and leaf veins. The flowers are relatively small, the petals 3-4 mm long. The tip of the corona have well-developed triangular projections on the edges. The horn-shaped secondary extension is flattened inside and ovate in outline. The subspecies Uncialis is limited to Arizona, Colorado, New Mexico, Oklahoma, Texas, Utah, Wyoming. It grows at 1500-2150 m altitude in open forests and desert scrub.
- Asclepias Uncialis subsp. ruthiae ( Maguire ) J.T.Kartesz & Gandhi. The shoots are 10 to 20 cm high with mostly broad - ovate, broadly elliptical or nearly round leaves which then gradually go up in narrow ovate or broadly lanceolate leaves. The edges are woolly hairy, the upper and lower sides short woolly hairy to glabrous. The flowers are relatively large, the Kronblattzipfel are 4-6 mm long. The tip of the corona have only vague to moderately developed triangular projections on the edges. The secondary extension on the inside of the tip of the corona is almost like fingers
The holotype is preserved at Utah State University. The subspecies ruthiae is limited to Arizona, New Mexico, Nevada and Utah. It grows in desert scrub and pinyon pine - juniper communities in 1100-1900 m altitude.