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Published In: Systema Naturae, Editio Decima 2: 1232. 1759. (Syst. Nat. (ed. 10)) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

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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4. Silphium perfoliatum L. (cup plant, cup rosinweed)

Pl. 289 e–h; Map 1229

Plants with rhizomes. Stems 100–250 cm long, solitary or more commonly appearing clustered, square in cross-section (strongly 4-angled), glabrous or rarely sparsely pubescent with relatively short (mostly 0.2–0.5 mm), slender hairs toward the base (at a few of the lowermost nodes), occasionally slightly glaucous. Leaves usually relatively thick but not or only slightly leathery, the upper surface moderately roughened with small pustules and sometimes also with sparse, minute hairs, the undersurface moderately to densely roughened-pubescent with a mixture of short and minute, spreading, mostly pustular-based hairs. Basal and lowermost stem leaves absent or withered at flowering, long-petiolate, the petioles often expanded into a pair of basal auricles, these wrapped around the stem and those of the stem leaves often more or less perfoliate, the blade 10–30 cm long, ovate to triangular-ovate, unlobed, tapered to a usually sharply pointed tip, tapered to angled at the base, the margins otherwise finely to coarsely toothed and with minute, more or less appressed hairs. Stem leaves progressively reduced from about the midpoint of the stem, opposite (the uppermost leaves rarely alternate), 3–35 cm long, the largest pairs of leaves with short to long, broadly winged petioles, these expanded toward the base and strongly perfoliate (fused into a leafy cup around the stem) or rarely not perfoliate, the median and upper leaves mostly short-petiolate to sessile. Inflorescences loose, open clusters or panicles, the heads long-stalked to short-stalked or nearly sessile. Involucral bracts 25–38, 12–27 mm long, elliptic to ovate, loosely ascending to somewhat spreading at the bluntly to sharply pointed tip, the outer surface usually glabrous, the margins with minute, ascending hairs. Receptacle 1.5–2.5 cm in diameter. Ray florets 18–35, the corolla 15–40 mm long. Disc florets numerous, the corolla 6–7 mm long, usually extending slightly beyond the tips of the chaffy bracts. Fruits 10–15 mm long, the surfaces glabrous, the angles with relatively broad, lighter wings (tapered toward the fruit base), each wing irregularly rounded and minutely hairy at the tip, the fruit with a broadly rounded apical notch. 2n=14. July–September.

Scattered nearly throughout the state but uncommon in the Mississippi Lowlands Division (eastern U.S. west to North Dakota and Oklahoma; Canada; introduced in Europe). Banks of streams and rivers, bottomland forests, and margins of ponds and lakes; also edges of crop fields, railroads, and roadsides.

Some botanists have divided S. perfoliatum into two varieties, but the utility in maintaining these is not evident. The var. connatum (L.) Cronquist (ssp. connatum (L.) Cruden), differs from var. perfoliatum in having at least the upper portion of the stem and the stalks of the heads with spreading hairs, sometimes longer (1–2 mm) hairs on the leaf undersurface, more of the leaves sessile, and often fewer (8–13) ray florets. It is said to occur in the mountains and Piedmont portions of North Carolina, Virginia, and West Virginia. However, Cruden (1962) reported slightly hairy (intermediate) plants from the extreme western and eastern portions of the species range and called these f. hornemannii (Schrad.) Cruden. Additionally, Steyermark (1963) included a rare Missouri variant from Stone County with only the uppermost leaves perfoliate, which he called f. petiolatum E.J. Palmer & Steyerm. Patterns of overall morphological variation within the species appear to be more complex than earlier authors have understood.

 


 

 
 
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