Vernonia

Detail of the inflorescence with basket- shaped partial inflorescences of Vernonia noveboracensis

The apparent asters or Vernonien ( Vernonia ) are a genus of flowering plants in the sunflower family ( Asteraceae). There are about 20 species (formerly were about 1000 species grouped in this genus ). All Types of today's close view ( according to H. Robinson 1999) of the genus are native to the New World; most species on the North American continent, only two or three species in South America and a kind in the Bahamas.

Description

Vegetative characteristics

The apparent asters are large, perennial herbaceous plants that can usually achieve growth heights of 20 to 200 cm, but also stature heights of more than 300 cm. Some species form rhizomes.

The stalked or sessile leaves are rarely predominantly in basal rosettes together, usually they are distributed on the stem. The shape of the leaf blades varies from ovate, elliptic, lanceolate, wrong - lanceolate, spatulate, linear or filiform. The base of the leaf blades, more or less wedge-shaped, except for the kind Vernonia pulchella with a rounded cut - sheet basis. The leaf edges are serrated usually, rarely entire, the blade tips are tapered to pointed. The leaf undersides are usually more or less scaly to finely tomentose to woolly stichborstig or, sometimes glabrous, usually covered with resin glands. The upper leaf surface is scaly or smooth, only sometimes covered with resin glands.

Generative features

In doldentraubigenn to total paniculate inflorescences with a diameter of (6 to ) 10 to 25 cm are usually 40 to 100, but also significantly less (6) or more flower heads, without bracts together. The bloom conditions are more or less stalked and discus shaped. The bracts are arranged to inverted bell-shaped cone-shaped or semi- spherical, 3 to 8, often to 11 or more inches in diameter. Every 18 to 70 bracts are in four to more than seven rows. The outer bracts are ovate to lanceolate or pfriemförmig, the inner more or less lanceolate to oblong. All are more or less papery, entire, often ciliate, the tips either rounded, then sometimes pointed, sharpened, pfriemförmig or thready. The surface is glabrous or slightly provided with fine bristles line up tomentose, sometimes studded with glands. In each flower heads are just depending on the type 9-30 (sometimes up to 65 or more) ray florets. The petals are fused into a tube, which is formed up to a tongue, it has five corolla lobes, what can clearly be seen that the corolla tube is formed from five petals. The petals are usually purple or pink, rarely white. The five corolla lobes are lanceolate - linear and shaped more or less the same.

The achenes are more or less columnar, sometimes arcuately curved. You have eight to ten ribs are glabrous or scaled up feinborstig and often staffed with resin glands. The constant pappus is composed of 20 to more than 30 outer, irregularly serrated to pfriemförmige scales or bristles, as well as 20 to more than 40 inner pfriemförmige to bristly scales or bristles.

The basic chromosome number is n = 17

System

The genus Vernonia was set up by the German botanist Johann Christian Daniel Schreber 1791 in Genera Plantarum, 2, p 541. The previously mentioned Serratula noveboracensis L. species was in André Michaux: Flora Boreali - Americana, 2, 1803, pp. 95 type species of Vernonia noveboracensis (L.) Michx .. The genus name honors the English botanist William Vernonia Vernon. Since the publication of Harold Ernest Robinson 1999 in the genus, only about 20 species included.

From only about 20 species occur in North America and Mexico, 17 species before:

Vernonia acaulis (Walter ) Gleason
Arkansas bill Aster ( Vernonia arkansana DC. ), Originating from southern North America, is cultivated in Europe as an ornamental plant.
Vernonia angustifolia Michx.
Vernonia baldwinii Torr.
Vernonia blodgettii Small
Vernonia fasciculata Michx.
Vernonia flaccidifolia Small
High note Aster ( Vernonia gigantea (Walter ) Trel. Branner & Coville ex )
Vernonia glauca (L.) Willd.
Vernonia larseniae B.L.King & S.B.Jones
Vernonia lettermannii Engelm. ex A. Gray
Vernonia lindheimeri A. Gray & Engelm.
New York bill Aster ( Vernonia noveboracensis (L.) Michx. It is native to the North American mainland and the Bahamas.
Vernonia pulchella Small
Vernonia sechellensis Baker
Vernonia texana ( A. Gray ) Small

From the earlier very large genera many species have been transferred to other genera, for example in the genera Baccharoides, Gymnanthemum and Lepidaploa.

Pictures

Vernonia fasciculata (English: Common Ironweed would = literally means " ordinary verbena " ):

Swell

John L. Strother: Vernonia in Flora of North America, Volume 19, 2006, p 206: Online. (Section Description and systematics)