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Published In: Novon 2(3): 270. 1992. (Novon) 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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7. Croton willdenowii G.L. Webster (common rushfoil)

Crotonopsis elliptica Willd.

Map 1662, Pl. 378 e–g

Plants monoecious, moderately to densely pubescent with small, peltate, scalelike trichomes (except on the upper surface of the leaf blades), these with a small, raised, brown attachment point and a relatively broad, thin, white body, the slender, stellate extensions forming a minute fringe around the margins, this appressed and not appearing fuzzy; the upper surface of the leaves with relatively dense, small, overlapping, stellate hairs, the often unequal branches 0.6–1.0 mm long. Stems 8–40 cm long, usually sparsely alternately branched. Leaves alternate, sessile or short-petiolate, the petiole without large, saucer-shaped glands at the tip. Leaf blades 0.7–2.0(–3.0) cm long, linear to narrowly ovate, angled or short-tapered at the base, rounded to angled or short-tapered to a usually sharply pointed tip, the margins entire, the undersurface paler than the upper surface. Inflorescences axillary, mostly short, loose spikes with 1 or 2 pistillate flowers at the base and several staminate flowers toward the tip. Staminate flowers with the calyx deeply (4)5-lobed, 0.8–1.1 mm long; the petals (4)5, 0.6–1.0 mm long, white; the stamens 4–6. Pistillate flowers with the calyx 0.8–1.1 mm long at flowering, becoming very slightly enlarged at fruiting, (4)5-lobed; the petals absent; the ovary 1-locular, the 3 styles shallowly 2-lobed toward the tip. Fruits 2.5–3.0 mm in length and diameter, elliptic to oblong-ovate in outline, slightly flattened, 1-seeded, indehiscent, thin-walled. Seeds 2.5–3.0 mm long, elliptic to oblong-ovate in outline, slightly flattened, the caruncle absent. June–September.

Scattered mostly south of the Missouri River (eastern U.S. west to Iowa, Kansas, and Texas). Glades, ledges and tops of bluffs, and openings of dry upland forests; also old fields; usually in nutrient-poor acidic soils.

This is the more widespread of the two rushfoils in Missouri. Previously, it and C. michauxii were classified into a separate genus of two species, Crotonopsis, based on their 1-seeded, indehiscent fruits. However, Webster (1992) argued that Crotonopsis represents merely a specialized subgroup within Croton related to the group of species that includes C. monthogynous, which has two-seeded fruits. In combining the genera, he found it necessary to coin replacement names for both species, as the original epithets from Crotonopsis already were in use for other species of Croton (C. ellipticus Geiseler and C. linearis Jacq.). Websters view has been supported by preliminary molecular phylogenetic analyses (Berry et al., 2005), in which the two species of former Crotonopsis are nested within a more derived lineage within Croton.



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