Erythea 3: 89. 1895.
Perennials, 40–150 cm (rhizomes creeping, short, stout). Stems erect, simple, moderately to sparsely soft-villous. Leaves basal and cauline; alternate; petiolate; blades 1-nerved, broadly to narrowly ovate, cordate, margins serrate, faces short-strigose. Heads discoid, in open paniculiform arrays. Involucres narrowly campanulate, (4–6 ×) 5–8 mm. Phyllaries 14–22 in 2–3 series, squarrose, 1-nerved (nerves translucent and swollen basally; ± keeled proximally), broadly lanceolate, unequal, ± foliaceous, margins scarious, faces moderately villoso-strigose. Receptacles flat, weakly pitted (ridges irregular), epaleate. Disc-florets 8–20, bisexual, fertile; corollas white or rose-purple-tinted, tubes longer than funnelform throats, lobes 5, spreading, lanceolate; style-branch appendages narrowly lanceolate (short-papillate). Cypselae mostly narrowly obconic to fusiform (not compressed), ribs 5–10, translucent, faces moderately appressed-strigose or glabrous; pappi persistent, of 35–50, ususally white, sometimes purplish (barb tips), barbellate bristles in 2 series (outer apically attenuate, slightly shorter and more numerous than inner, strongly clavate bristles). x = 9.
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The generic position of the monotypic Brintonia has been ambiguous since it was first described. The lack of ray florets left open to speculation what color they might have been before evolutionary reduction. Elliott presumably assumed that they were blue or white, and tentatively placed it in Aster. J. Torrey and A. Gray (1838–1843, vol. 2, p. 195) assumed that they had been yellow, and placed the species in Solidago. Greene emphasized differences in foliage, capitulescence, corolla, and pappus features, and created the monotypic Brintonia for the species. L. C. Anderson and J. B. Creech (1975) found no special anatomic features of the mesic plant. A. Cronquist (1980) accepted generic status for Brintonia. G. L. Nesom (1991d, 1993b) believed that it is closely related to S. bicolor in Solidago subsect. Albigula. It is more similar to S. sphacelata and S. auriculata in basal leaf and array features but is not more closely related to those than to S. bicolor. Cypsela, phyllary midnerve, and floret and pappus pigmentation features indicate a position outside Solidago, as do DNA data (J. B. Beck et al. 2004). The phylogenetic position of B. discoidea remains uncertain within Solidagininae.
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