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Published In: Skrifter af Naturhistorie-Selskabet 2(2): 29, pl. 4. 1793. (Skr. Naturhist.-Selsk.) Name publication detail
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native

 

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1. Rudbeckia amplexicaulis Vahl (clasping coneflower)

Dracopis amplexicaulis (Vahl) Cass.

Pl. 276 b; Map 1217

Plants annual, with taproots. Stems 20–70(–90) cm long, glabrous, occasionally slightly glaucous. Leaves all unlobed, all (except sometimes the basal ones) strongly cordate at the base and clasping the stem, the margins entire or bluntly and usually finely toothed, the surfaces glabrous, smooth, usually somewhat glaucous, appearing bluish green when fresh. Basal and lowermost stem leaves usually absent at flowering, long-petiolate to nearly sessile, the blade 2–15 cm long, 6–15 mm wide, oblanceolate to oblong-oblanceolate, rounded to sharply pointed at the tip. Median and upper stem leaves sessile, the blade 1–10 cm long, 8–40 mm wide, progressively shorter and broader, oblong-ovate to oblong-obovate, ovate or heart-shaped, tapered to a sharply pointed tip. Inflorescences mostly appearing as loose, open clusters of heads, sometimes of solitary heads. Involucral bracts 7–12, 3–10 mm long, linear to lanceolate, glabrous. Receptacle 10–30 mm long, 8–15 mm in diameter, hemispherical to somewhat ovoid at the start of flowering, then elongating and becoming ovoid to conical. Chaffy bracts subtending the ray and disc florets, shorter than the disc florets, broadly angled or abruptly short-tapered to a usually sharply pointed tip, the outer surface glabrous, the margins with a fringe of minute, spreading hairs. Ray florets 6–10(–12), the corolla 12–30 mm long, relatively broad, strongly reflexed at flowering, yellow, sometimes strongly reddish- or orangish-tinged toward the base, the outer surface moderately to densely short-hairy. Disc florets numerous, the corolla 2.5–3.5 mm long, greenish yellow to yellow toward the base, dark purple to brownish purple toward the tip, the lobes usually strongly curled downward at flowering. Stigma lobes elongate and more or less sharply pointed at the tip. Pappus absent or occasionally a minute rim or crown. Fruits 1.8–2.5 mm long. 2n=32. May–July.

Uncommon in Jasper and Newton Counties, also introduced there and elsewhere in western Missouri as well as the city of St. Louis (southern [mostly southeastern] U.S. north to Kansas and Missouri; introduced sporadically farther north). Upland prairies and glades; also edges of crop fields, railroads, roadsides, and open, disturbed areas.

Steyermark (1963) treated R. amplexicaulis (as Dracopis) as native in Missouri, and the oldest specimens, from Jasper and Newton Counties (collected by E. J. Palmer in 1909), apparently were collected from native plant communities. The species also grows natively in adjacent portions of Oklahoma and Kansas. However, most of the historical materials and all of the more recent collections undoubtedly represent introduced populations. Clasping coneflower is cultivated as an ornamental in gardens and can escape to form extensive populations in disturbed habitats. It also has been planted along some highways as a component of wildflower seed mixes for so-called roadside beautification projects.

The classification of this species remains somewhat controversial. Steyermark (1963) and most earlier authors maintained it as the only species of Dracopis Cass. This interpretation was supported by the phylogenetic analysis of morphological and anatomical characters in the various coneflower genera of Cox and Urbatsch (1990), who concluded that the genus is a relative of Ratibida. Molecular phylogenetic studies of the coneflower genera involving restriction site variation within the chloroplast genome was inconclusive but weakly favored a similar interpretation (Urbatsch and Jansen, 1995). However, an expanded molecular study that integrated the earlier chloroplast genomic data with nuclear sequence data resolved Dracopis as a distinct lineage nested within Rudbeckia (Urbatsch et al., 2000). Urbatsch and his colleagues favored a classification in which Dracopis is treated as one of three subgenera within Rudbeckia. This classification is followed in the present treatment.

 
 


 

 
 
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