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EUPHORBIACEAE SPURGE FAMILY

Mark H. Mayfield & Grady L. Webster, except as noted

Annual to shrub, tree [vine, cactus-like succulent]; monoecious or dioecious; sap clear or milky. Stem: generally branched [fleshy or spiny]. Leaf: generally simple, alternate to whorled, generally stipuled, sessile or petioled; blade entire, toothed, or lobed. Inflorescence: flowers solitary or in terminal or axillary cymes, racemes, spikes, or panicles, or (in Euphorbia) 1° inflorescence a compact, flower-like cyathium with much-reduced flowers enclosed within an involucre of fused bracts, cyathia terminal or axillary, 1 or in cyme-like arrays. Flower: unisexual, ± radial; sepals 0 or 2–6, free or fused; petals generally 0(5); stamens 1–many, free or filaments fused; ovary superior, chambers (1)3(4), styles free or fused, undivided, forked, or variously lobed. Fruit: generally capsule that splits into mericarps that then dehisce, releasing seeds. Seed: 1 per chamber; knob-like appendage sometimes present at attachment scar.
217 genera, 6000+ species: ± worldwide especially tropics; some cultivated (Aleurites, tung oil; Euphorbia species; Hevea, rubber; Ricinus). Many species ± highly TOXIC, due primarily to latex, especially if eaten or in contact with skin, eyes. [Yang et al. 2012 Taxon 61:764–789] Eremocarpus moved to Croton, Tetracoccus moved to Picrodendraceae for TJM2; Chamaesyce moved to Euphorbia here (key to genera revised by Thomas J. Rosatti). —Scientific Editor: Bruce G. Baldwin.

Key to Euphorbiaceae

EUPHORBIA SPURGE

David J. Keil, Thomas J. Rosatti, Mark H. Mayfield & Daryl Koutnik

Annual to shrub [tree; fleshy, ± cactus-like], glabrous or hairy; sap milky; generally monoecious. Stem: prostrate to erect, generally < 1 m; branches arrayed around main stem(s) in 3-dimensions or 2-ranked, resulting in 2-faced stems with adaxial leaf faces all displayed to top side and abaxial leaf faces to bottom side. Leaf: proximal cauline, alternate or opposite, ± sessile to petioled; distal-most cauline in some species whorled, subtending umbel-like cluster of inflorescence branches, leafy bracts distal to whorled leaves generally opposite (whorled); stipules 0, gland-like, thread-like, or scale-like, free or fused, entire to divided; blade entire or toothed (pinnately lobed), base symmetric or asymmetric. Inflorescence: 1° inflorescence a cyathium, resembling a flower; cyathia 1–many, stalked or sessile, terminal (axillary), in generally leafy-bracted cyme-like arrays; cyathium a compact unit comprising an involucre of 5 fused bracts enclosing 1–many reduced staminate flowers and 1(0) pistillate flower; involucre generally 1–5 mm, bract tips alternate with 1–5 nectary glands (derived from modified stipules of involucral bracts), these transversely crescent-shaped or oblong to ± round, flat to cup-like, entire, toothed, or with 2 horn-like lobes, with or without distal, white to pink or red, flat, petal-like appendages; bractlets within involucre membranous or thread-like, often fringed. Staminate flower: (1–4)5–many, generally in 5 clusters around pistillate flower (this difficult to observe); calyx 0; each staminate flower a single stamen jointed to tip of a thread-like pedicel; pedicel persistent, stamen deciduous after pollen released. Pistillate flower: (0)1, central, stalked; calyx 0; ovary chambers 3, styles 3, free or fused at base, undivided or ± deeply forked. Fruit: stalk generally elongating, generally curved, pushing developing fruit from involucre; capsule ± spheric to ovoid or oblong, in ×-section ± round to 3-lobed or -angled. Seed: ± round or ± 3- or 4-angled (flattened) in ×-section, smooth or sculptured; knob-like appendage at attachment scar present or 0.
± 1750 species: warm and/or dry temperate to tropics worldwide. Euphorbus, physician to the King of Mauritania, 1st century [Horn et al. 2012 Molec Phylogen Evol 63:305–326] Forms monophyletic group with Chamaesyce, included here. Euphorbia serrata L. <Noxious weed> considered extirpated from California; 2003 report that Euphorbia exigua L. is possibly naturalizing as yet unconfirmed; Euphorbia marginata Pursh occasionally persisting from gardens, but recent records lacking. Euphorbia graminea Jacq. <Noxious weed> an urban weed. For fruit, seeds, "in ×-section" indicated only if not lobed or angled.
Unabridged references: [Wheeler 1936 Bull S Calif Acad Sci 35:127–147]

Key to Euphorbia

E. vallis-mortae (Millsp.) J.T. Howell DEATH VALLEY SANDMAT
NATIVE
Perennial herb, densely short-soft-hairy or stem becoming glabrous. Stem: prostrate to decumbent, repeatedly forking, 2-faced. Leaf: opposite throughout, 2-ranked, subsessile; bottom-side stipules fused, top-side stipules free, thread-like; blade 4–6 mm, oblong to ovate, entire, base asymmetric, tip obtuse. Inflorescence: cyathia 1 per node or in small clusters at branch tips; involucre 2–2.5 mm, bell-shaped; glands 4, < 1 mm, transversely oblong or elliptic, green to yellow or ± red; petal-like appendage as wide as to wider than gland, entire to irregularly toothed, white. Staminate flower: 17–22. Pistillate flower: style forked 1/2. Fruit: 2 mm, ovoid, lobed. Seed: < 2 mm, ovoid, 4-angled, smooth, white; knob 0.
Dry, sandy places; < 1300 m. East of Sierra Nevada, Mojave Desert. [Chamaesyce vallis-mortae Millsp.] May–Oct [Online Interchange] {CNPS listed}

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Oct 1 2014
Citation for this treatment: [Author of taxon treatment] 2013. Euphorbia, Revision 1, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=25516, accessed on Oct 1 2014

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Geographic subdivisions indicated for the distribution of Euphorbia vallis-mortae Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.