Milkweed Blossoms

by Bruce Bley

Title

Milkweed Blossoms

Artist

Bruce Bley

Medium

Photograph - Photography

Description

Asclepias L. (1753), the milkweeds, is a genus of herbaceous perennial, dicotyledonous plants that contains over 140 known species. It previously belonged to the family Asclepiadaceae, but this is now classified as the subfamily Asclepiadoideae of the dogbane family Apocynaceae.Milkweed is named for its milky juice which consists of a latex containing alkaloids and several other complex compounds including cardenolides. Some species are known to be toxic.
Carl Linnaeus named the genus after Asclepius, the Greek god of healing, because of the many folk-medicinal uses for the milkweed plants.Pollination in this genus is accomplished in an unusual manner. Pollen is grouped into complex structures called pollinia (or "pollen sacs"), rather than being individual grains or tetrads, as is typical for most plants. The feet or mouthparts of flower-visiting insects such as bees, wasps and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia then mechanically attach to the insect, pulling a pair of pollen sacs free when the pollinator flies off. Pollination is effected by the reverse procedure in which one of the pollinia becomes trapped within the anther slit.
Asclepias species produce their seeds in follicles. The seeds, which are arranged in overlapping rows, have white, silky, filament-like hairs known as pappus, silk, or floss. The follicles ripen and split open, and the seeds, each carried by several dried pappi, are blown by the wind. They have many different flower colorations.
Milkweeds are an important nectar source for bees and other nectar-seeking insects, and a larval food source for monarch butterflies and their relatives, as well as a variety of other herbivorous insects (including numerous beetles, moths, and true bugs) specialized to feed on the plants despite their chemical defenses.
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July 9th, 2014

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