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FNA | Family List | FNA Vol. 12 | Euphorbiaceae

24e. Euphorbia Linnaeus sect. Nummulariopsis Boissier in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 15(2): 71. 1862.

Victor W. Steinmann

Jess A. Peirson

Herbs, perennial [rarely annual], with slender to thickened, usually erect, occasionally spreading, rootstock. Stems erect or ascending [prostrate], branched or unbranched, terete, glabrous [hairy]. Leaves alternate [opposite]; stipules absent [present, at base of petiole]; petiole absent or indistinct; blade dimorphic (at proximal 2–4 nodes triangular and much smaller than at distal nodes) [monomorphic], base symmetric, margins entire, surfaces glabrous; venation pinnate, midvein often prominent. Cyathial arrangement: terminal pleiochasia with 2–5 primary branches; individual pleiochasial branches 2-branched at each node; bracts subtending pleiochasia (pleiochasial bracts) whorled, green, similar in shape but slightly smaller than distal stem leaves, those on branches and subtending cyathia (dichasial and subcyathial bracts) opposite, distinct; additional cymose branches occasionally present in axils of distal leaves, but alternately arranged and without whorled bracts. Involucre ± actinomorphic, not spurred; glands 5, flat or slightly convex; appendages absent. Staminate flowers [10–]20–30. Pistillate flowers: ovary glabrous, subtended by calyxlike structure; styles connate 1/8–1/2 length, 2-fid apically. Seeds: caruncle absent.

Species ca. 30 (4 in the flora): se United States, South America.

Section Nummulariopsis belongs to subg. Euphorbia and has a disjunct distribution, with species native to the southeastern United States and to temperate and subtropical areas of southern South America. In the flora area, the species are restricted to sandy habitats from Florida and southern Georgia to southern Mississippi. All species are adapted to sandy pinelands or scrub vegetation characterized by wide fluctuations in soil moisture and periodic, recurrent natural fires (E. L. Bridges and S. L. Orzell 2002).

In the key and descriptions that follow, leaf refers to the leaves at mid and distal nodes.

SELECTED REFERENCE Bridges, E. L. and S. L. Orzell. 2002. Euphorbia (Euphorbiaceae) section Tithymalus subsection Inundatae in the southeastern United States. Lundellia 5: 59–78.

1 Leaf blades linear, linear-elliptic, linear-lanceolate, or lanceolate, length 7+ times width, largest 15 mm wide or less (usually less than 10 mm wide)   (2)
+ Leaf blades elliptic, narrowly elliptic, narrowly oblong, or obovate, length less than 6 times width, largest usually 16+ mm wide   (3)
2 (1) Peduncles (except for that of 1st cyathium at base of pleiochasia) 2–5 mm, not exceeding dichasial bracts; seeds depressed-globose, wider than long.   126 Euphorbia floridana
+ Peduncles 6–24 mm, often exceeding dichasial bracts; seeds ovoid-globose, longer than wide.   127 Euphorbia inundata
3 (1) Involucres 2.4–3.6 × 2.5–3.6 mm; styles 3.3–3.6 mm, connate 1/2 length; Highlands County, c peninsular Florida   128 Euphorbia rosescens
+ Involucres 1.3–2.3 × 1.6–2.5 mm; styles (1–)1.3–1.5 mm, connate 1/4 length; Bay, Franklin, and Gulf counties, ec Florida panhandle.   129 Euphorbia telephioides


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