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FNA | Family List | FNA Vol. 12 | Euphorbiaceae

20. Croton michauxii G. L. Webster, Novon. 2: 270. 1992.
[E F]

Rushfoil Rushfoil

Crotonopsis linearis Michaux, Fl. Bor.-Amer. 2: 186, plate 46. 1803

Herbs, annual, 1–9 dm, monoecious. Stems usually single from base, much branched from near middle, densely stellate-lepidote appearing silvery. Leaves not clustered; stipules rudimentary; petiole 0.1–0.5 cm, glands absent at apex; blade lanceolate-linear to ovate-lanceolate, 1.5–4 × 0.1–0.4(–1.5) cm, base acute to cuneate, margins entire, apex acute, abaxial surface silvery, stellate-lepidote, adaxial surface green, sparsely stellate-hairy, hairs with few radii. Inflorescences bisexual, spikes, 0.3–3 cm, staminate flowers 1–12, pistillate flowers 1–6. Pedicels: pistillate absent, staminate 0–1 mm. Staminate flowers: sepals 5, 1 mm, abaxial surface lepidote; petals 5, spatulate, 0.6–1 mm, abaxial surface glabrous except margins villous; stamens 5–7. Pistillate flowers: sepals (4–)5, equal, 1–1.5 mm, margins entire, apex straight, abaxial surface lepidote; petals 0; ovary 1-locular; styles 3, 0.5–0.8 mm, minutely 2-fid, terminal segments 3 or 6. Achenes 2.5–3 × 1–1.2 mm, smooth; columella absent. Seeds 2–2.5 × 1 mm, surface not visible because seed coat adherent to fruit wall.

Varieties 2 (2 in the flora): United States.


1 Inflorescences 1–3 cm; achenes usually 3–6, densely stellate-lepidote, hairs ± spreading, radii separate most of length, umbos usually sharp, sometimes rounded; leaf blade adaxial surface hairs not overlapping.   20a Croton michauxii var. michauxii
+ Inflorescences usually less than 1 cm; achenes 1–2, sparsely stellate-lepidote, hairs appressed, radii joined most or all of length, umbos usually blunt, rarely sharp; leaf blade adaxial surface hairs overlapping near midvein.   20b Croton michauxii var. elliptica

Lower Taxa


 

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