Asclepias glaucescens
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Asclepias glaucescens |
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| Asclepias glaucescens | ||||||||||||
| Kunth |
Asclepias glaucescens (Eng. Nodding Milkweed ) is a species of the genus silk plants ( Asclepias ) from the subfamily of the silk plants (Asclepiadoideae).
features
Vegetative characteristics
Asclepias glaucescens is an herbaceous , perennial plant with a deeply rooted, fleshy rhizome. The more or less erect, or ascending, bare stems are mostly unbranched and stiff. They reach heights of 15 to 80 cm. The leaves are opposite and sessile (or sessile), or with very short, maximally 2 mm long stalks. The slightly succulent leaf blades are broad-egg-shaped, egg-shaped to narrowly elongated-egg-shaped, and 3 to 18 cm long, 1 to 7 cm wide. The spade tip (apex) is broadly pointed to rounded, often with an attached tip (mucronat). The base is heart-shaped and more or less clearly surrounds the stem (amplexicaul). The edges are usually wavy.
Inflorescence and flowers
The inflorescences are solitary and arise laterally at a few of the upper nodes , only occasionally they also develop terminally. They are spherical and have few to many flowers. The shafts are stiff, 2 to 20 cm long and finely hairy. The inflorescences stand upright, occasionally also inclined or slightly drooping. They are hemispherical on top and have a diameter of 5 to 7 cm. The flower stalks are also rather stiff and 1 to 3.5 cm long. The hermaphroditic flowers are five-fold and zygomorphic ; they have a double flower envelope. The flowers are comparatively large. The sepals are ovate-lanceolate and 4 to 5 mm long. The petals are wheel-shaped and strongly bent back. They are greenish-cream-colored, often pink or reddish in color and 8 to 12 mm long. The gynostegium has a short stalk or almost sessile. The stem is broad-cylindrical, about 1 mm high and 2 mm wide. The yellowish petals are turned inward at the margins; they form a J-shaped, sack-like structure that initially runs horizontally at the base, then bends upwards. The upper edge runs horizontally and is narrowed at the side. These heavily modified minor corolla lobes are 5 to 7 mm long and 2 to 4 mm wide at the top. They are slightly shorter than the gynostegium. The horn-shaped appendages are laterally flattened, sickle-shaped and lie almost completely on the. They are rather short and protrude only a little from the pocket-like corolla lobes; they are therefore only slightly inclined over the stylus head. The stylus head is short-cylindrical, about 3 mm long and 3 to 4 mm wide. The pollinia are 1.1 to 1.3 mm long with a 0.8 to 1 mm long corpusculum. The wings of the stamens are 2.4 to 2.8 mm long.
Fruits and seeds
The superficially smooth and bare follicles stand upright on curved stems. They are slender-spindle-shaped, 8 to 10 cm long (11-15 cm) and about 1 cm thick. The seeds are broadly ovate and 6 to 8 mm long. The white head of hair is 2.5 to 3.5 cm long.
Similar species
Asclepias glaucescens is similar to Asclepias amplexicaulis . The latter type, however, has a pedunculated gynostegium. However, the two species do not occur together. Asclepias elata is almost indistinguishable from Asclepias glaucescens without flowers . However, the flowers show a number of differences. So has Asclepias elata only weakly developed horn-like extensions and a sessile Gynostegium, while the projections in Asclepias glaucescens are clearly formed and the Gynostegium is stalked. An additional distinguishing feature can be found in the pollinium. In Asclepias elata there are two hyaline appendages of the gland above the insertion of the translator arms; in Asclepias glaucescens these appendices are missing. However, the two types can hybridize.
Geographical distribution and ecology
The range of the species extends from the south of the USA (western Texas, Arizona and New Mexico), over Mexico to Guatemala, El Salvador and Costa Rica.
The species grows in ravines, rocky stream beds, open forest areas, in dry pine-oak forests or pine-juniper forests at 1200 to 2150 m above sea level.
The flowering period is from June to September.
Taxonomy and systematics
The taxon was first described by Karl Sigismund Kunth in 1819 .
supporting documents
literature
- Robert E. Woodson, Jr .: The North American Species of Asclepias L. In: Annals of the Missouri Botanical Garden , Vol. 41, No. 1, 1954, pp. 1-211, St. Louis, Mo. URL , pp. 97-98.
Individual evidence
- ↑ a b c SEINet Arizona - New Mexico Chapter: Asclepias glaucescens Kunth
- ↑ Friedrich Wilhelm Heinrich Alexander von Humboldt, Aimé Jacques Alexandre Bonpland, Karl Sigismund Kunth: Nova genera et species plantarum, quas in peregrinatione ad plagam æquinoctialem orbis novi, collegerunt, descripserunt, et partim adumbraverunt, Am. Bonpland and A. de Humboldt. Volume 3, plate 227, Paris 1819 (11th delivery: July 9, 1819) www.plantillustrations.org