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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

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. <WEEDINESS SYMBOL 1> 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. <WEEDINESS SYMBOL 1> 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

1. Proximal leaves alternate, bases generally symmetric

2. Involucre gland appendage petal-like, white; shrub ..... E. misera

2' Involucre gland appendage 0; annual to perennial herb (E. dendroides a shrub)

3. Involucre glands 1–3, less often 4(5), ± cupped

4. Involucre, fruit densely hairy; seed oblong, flattened ..... E. eriantha

4' Involucre, fruit generally glabrous or ± so; seed ellipsoid to oblong or ovoid, not flattened

5. Bracts subtending cyathia each red proximally, green distally; stem glabrous ..... [E. cyathophora]

5' Bracts subtending cyathia each green or ± white proximally or throughout; stem hairy or glabrous

6. Hairs recurved on distal stems, abaxial leaf faces; seed >= 2.2 mm wide, coarsely tubercled ..... [E. davidii] (2)

6' Hairs ± straight, spreading on distal stems, abaxial leaf faces; seed <= 2.1 mm wide, finely tubercled ..... [E. dentata] (2)

3' Involucre glands 4(5), ± flat

7. Leaf margin finely to coarsely toothed

8. Leaf tip ± acute ..... E. terracina

8' Leaf tip rounded, obtuse, or notched

9. Perennial herb; stem densely hairy ..... E. oblongata

9' Annual; stem glabrous or sparsely hairy

10. Whorled inflorescence branches 5; fruit smooth; staminate flowers 8–15 ..... E. helioscopia

10' Whorled inflorescence branches 3; fruit tubercled especially near tip and on lobes; staminate flowers 5–10 ..... E. spathulata

7' Leaf margin generally entire (± entire to minutely crenate)

11. Shrub ..... E. dendroides

11' Annual to per

12. Annual (biennial)

13. Fruit lobes 2-keeled ..... E. peplus

13' Fruit lobes not keeled ..... E. crenulata

12' Perennial herb

14. Seed smooth

15. Seed ± white; leaves lanceolate ..... [E. rigida]

15' Seed gray to tan or ± brown; leaves linear to (ob)lanceolate ..... E. virgata

14' Seed rarely smooth

16. Seed with ± worm-like papillae (smooth), gray-brown; leaves obovate to ± round ..... [E. myrsinites]

16' Seed generally pitted or surface shallowly net-like, occasionally ± smooth; leaves elliptic to (ob)ovate or spoon-shaped

17. Leaf sessile; stem ascending to erect; gland shortly 2-horned, entire to scalloped between horns ..... E. lurida

17' Leaf ± sessile to short petioled; stem decumbent to erect; gland transversely obovate or fan-shaped, scalloped or incised but not 2-horned ..... E. schizoloba

1' Proximal leaves opposite

18. Leaves 4-ranked on proximal stem, bases symmetric; stems not forked, not 2-faced

19. Distal cauline leaves alternate

20. Hairs recurved on distal stems, abaxial leaf faces; seed >= 2.2 mm wide, coarsely tubercled ..... [E. davidii] (2)

20' Hairs ± straight on distal stems, abaxial leaf faces; seed <= 2.1 mm wide, finely tubercled ..... [E. dentata] (2)

19' Distal cauline leaves opposite or whorled

21. Glands of involucre transversely oblong, without horn-like lobes, white petal-like appendages present; leaves serrate; 1° inflorescence branches not whorled; fruit 2.5–3.4 mm ..... E. exstipulata var. exstipulata

21' Glands of involucre crescent-shaped, with 2 horn-like lobes, petal-like appendages 0; leaves entire; 1° inflorescence branches whorled; fruit 8–15 mm ..... E. lathyris

18' Leaves 2-ranked, bases generally asymmetric; stems repeatedly forked, 2-faced

22. Glands of involucre without white to pink or red petal-like appendages (appendages ± 0 on some glands in E. pediculifera)

23. Perennial herb

24. Fruit glabrous ..... E. parishii

24' Fruit hairy ..... E. pediculifera (3)

23' Annual

25. Fruit hairy

26. Involucre < 1 mm, glands << 0.5 mm; staminate flowers 2–5; fruit < 1.5 mm ..... E. micromera (2)

26' Involucre 1.5–2 mm, glands 0.5 mm; staminate flowers 22–25; fruit 2 mm ..... E. pediculifera (3)

25' Fruit glabrous

27. Leaf linear, base ± symmetric; stem proximally erect ..... E. revoluta (2)

27' Leaf oblong, lanceolate to (ob-)ovate to round, base asymmetric; stem prostrate to decumbent

28. Seed ± 2-angled, flattened, smooth; involucre glands transversely obovate ..... E. platysperma

28' Seed 3–4-angled, not flattened, smooth, wrinkled, or transversely ridged; involucre glands round or transversely elliptic

29. Fruit < 1.5 mm; seed 1–1.5 mm; staminate flowers 2–5 ..... E. micromera (2)

29' Fruit 2–2.5 mm; seed 1.5–2 mm; staminate flowers 40–60 ..... E. ocellata

30. Leaf <= 15 mm, lanceolate to ovate; Desert ..... subsp. arenicola

30' Leaf < 10 mm, ovate to sickle-shaped; California Floristic Province (except Peninsular Ranges) ..... subsp. ocellata

22' Glands of involucre with white to pink or red petal-like appendages (appendages ± 0 on some glands in E. pediculifera)

31. Cyathia generally in dense axillary cyme-like clusters, occasionally 1 per node; leaves 8–35 mm; stem generally ± erect (decumbent) ..... E. nutans

31' Cyathia 1 per node, occasionally dense on lateral branches or 1 at branch tips; leaves 1–40 mm; stem prostrate to ascending, occasionally erect

32. Fruit glabrous; stem, leaves, involucre generally glabrous (stem, leaves glabrous to hairy in E. abramsiana)

33. Stipules fused into wide, membranous scale

34. Perennial herb; fruit 2–2.5 mm; staminate flowers 15–30 ..... E. albomarginata

34' Annual; fruit ± 1.5 mm; staminate flowers 3–8(10) ..... E. serpens

33' Stipules free or fused, but not a wide, membranous scale

35. Perennial herb

36. Fruit, seed 2–2.5 mm; proximal stipules free ..... E. fendleri

36' Fruit, seed 1–1.5 mm; proximal stipules free or fused ..... E. polycarpa (2)

35' Annual

37. Leaves linear, base ± symmetric; stem prostrate to erect

38. Involucre glands 1–4, ovate, appendage narrower than gland; fruit, seed ± 2 mm; seed smooth; stem prostrate to ascending ..... E. parryi

38' Involucre glands ± 4, ± round, appendage wider than gland; fruit, seed <= 1.5 mm; seed transversely ridged; stem proximally erect ..... E. revoluta (2)

37' Leaves elliptic, oblong, lanceolate, ovate, round, or spoon-shaped, base asymmetric; stem prostrate to decumbent

39. Leaf margin entire ..... E. abramsiana (2)

39' Leaf margin toothed, at least toward tip, sometimes finely so

40. Styles simple; involucre gland appendages deeply 3–5-lobed ..... E. hooveri

40' Styles divided; involucre gland appendages entire, scalloped, or shallowly lobed

41. Stem subglabrous to hairy; seed transversely 4–6-ridged ..... E. abramsiana (2)

41' Stem glabrous; seed transversely 3–4-ridged or smooth to wrinkled

42. Seed transversely 3–4-ridged; involucre gland appendage wider than gland ..... E. glyptosperma

42' Seed smooth to wrinkled; involucre gland appendage narrower than gland ..... E. serpyllifolia subsp. serpyllifolia

32' Fruit with hairs, at least on lobes; stem, leaves, involucre generally with hairs

43. Perennial herb or shrub

44. Plant soft glandular-hairy with jointed hairs; staminate flowers 5–10; involucre urn-shaped — Sonoran Desert ..... E. arizonica

44' Plant puberulent to finely tomentose, strigose, or short-stiff-hairy with non-jointed hairs; staminate flowers >= 15; involucre urn- or bell-shaped or obconic

45. Seed 3-angled, ridged transversely ..... E. pediculifera (3)

45' Seed 0- or 4-angled (sometimes ± 3-angled in E. jaegeri), smooth to wrinkled or irregularly dimpled or faintly ridged transversely

46. Leaf hairs straight

47. Shrub; involucre gland appendage wider than gland, irregularly divided from halfway to ± base into 4–8 ± triangular to awl-shaped segments ..... E. jaegeri

47' Perennial herb; involucre gland appendage narrower to wider than gland, entire to scalloped ..... E. polycarpa (2)

46' Leaf hairs not straight

48. Involucre 1–1.5 mm; glands dark red to ± black ..... E. melanadenia

48' Involucre 2–2.5 mm; glands green to yellow or ± red ..... E. vallis-mortae

43' Annual

49. Involucre 1.5–2 mm; fruit 2–2.5 mm; staminate flowers 40–60 ..... E. ocellata subsp. rattanii

49' Involucre < 1.5 mm; fruit 1–2 mm; staminate flowers < 20

50. Involucre gland appendage deeply 3–5-lobed; involucre urn-shaped ..... E. setiloba

50' Involucre gland appendage entire to scalloped; involucre bell-shaped or obconic

51. Fruit 1.5–2 mm; seed wrinkled; involucre gland appendage narrower than gland ..... E. serpyllifolia subsp. hirtula

51' Fruit <= 1.5 mm; seed transversely ridged or wrinkled; involucre gland appendage as wide as to wider than gland

52. Seeds transversely wrinkled; fruit evenly strigose; involucre gland appendage as wide as gland ..... E. maculata

52' Seeds transversely ridged; fruit hairy only on lobes; involucre gland appendage as wide as to wider than gland ..... E. prostrata

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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