Key to the genera of the Heliantheae

1.

Capitula unisexual with male and female florets in separate capitula on same plant

2

 

Capitula all bisexual, all alike, both male and female florets in each capitulum or disc florets hermaphrodite

3

2. (1)

Female capitula with 1 floret, smooth to rugose or verrucose outside, with one apical beak

Ambrosia

2.

Female capitula with 2 florets, covered outside with hooked spines with 2 apical beaks

Xanthium

3. (1)

Achenes (at least central) with pappus of retrorsely barbed awns

4

 

Achenes lacking retrorsely barbed awns, pappus segments often antrorsely scabrid or plumose or absent

7

4. (3)

Ray achenes obovate, without awns; disc achenes elongate, mostly beaked and with awns

Heterosperma

 

Ray and disc achenes mostly alike, all with similar pappus

5

5. (4)

Lianas; pappus awns clustered in 2 groups on apical lobes of achenes

Ericentrodea

 

Plants mostly erect or decumbent; pappus awns not clustered

6

6. (5)

Anther filaments pubescent; achenes rostate, usually quadrangular and furrowed

Cosmos

 

Anther filaments glabrous; achenes erostrate, not furrowed or irregularly furrowed

Bidens

7. (3)

Leaf lamina, sometimes phyllaries or even corollas with obvious included glandular dots

8

 

Leaf lamina and other parts lacking included glandular dots, with glandular dots on surface, glandular-stipitate or eglandular

11

8. (7)

Phyllaries connate into tube, sometimes splitting with age

Tagetes

 

Phyllaries free (rarely connate only at very base), separately attached to receptacle

9

9. (8)

Phyllaries biseriate; capitula calyculate; pappus of squamellae markedly divided into coarsely barbellate flattened setae

Dyssodia

 

Phyllaries uniseriate; capitula ecalyculate; pappus of hair-like setae or of aristate squamellae

10

10. (9)

Capitula radiate; phyllaries articulated at base; leaf bases distinctly ciliate, sessile, bases only slightly narrowed

Pectis

 

Capitula discoid; phyllaries not articulate at base; leaves lacking basal cilia, distinctly petiolate or sessile

Porophyllum

11. (7)

Capitula axillary, solitary, sessile; paleae tightly conduplicate about achenes; plants aquatic or of marshy areas

Enydra

 

Capitula terminal, or if axillary or solitary distinctly pedicellate; paleae, when present, not tightly conduplicate about achenes; plants of various habitats, rarely of marshy areas

12

12. (11)

Disc florets functionally male, often with undivided style arms; disc achenes undeveloped

13

 

Disc florets hermaphrodite with functional style arms; disc achenes fertile

18

13. (12)

Ray achenes completely enclosed in spiny phyllaries

Acanthospermum

 

Ray achenes not enclosed in spiny phyllaries

14

14. (13)

Ray achenes with marginally attached paleae

Parthenium

 

Ray achenes without marginally attached paleae

15

15. (14)

Female floret corollas tubular, with minute limb or small lobules

16

 

Female floret corollas with enlarged limb

17

16. (15)

Inflorescences usually of numerous loosely aggregated capitula; phyllaries and paleae without obvious longitudinal resin ducts; achenes without furrows or ribs; plants shrubs or small trees

Clibadium

 

Inflorescences usually of many capitula in dense terminal glomerules; phyllaries and paleae with obvious resin ducts; achenes with obvious furrows or ribs; plants perennial herbs or subshrubs to shrubs

Ichthyothere

17. (15)

Phyllaries distinctly biseriate, outer series spreading and foliaceous, inner enclosing ray achenes with large glandular-stipitate glands on outer surface; petioles broad and partly or completely winged

Smallanthus

 

Outer phyllaries not large and foliaceous, inner phyllaries subtending ray achenes without stipitate-glands on outer surface; petioles slender and wingless

Baltimora

18. (12)

Florets in capitula or capitula-like structures individually surrounded by radially symmetrical bracts, sometimes considered compound heads of many single-flowered capitula

Lagascea

 

Florets in heads or head-like structures not surrounded with radially symmetrical bracts; capitula with 2 or more florets

19

19. (18)

Ray florets absent or sterile, not female

20

 

Ray florets fertile, female

38

20. (19)

Plants resinous

Flourensia

 

Plants not resinous

21

21. (20)

Achenes prismatic or broadly quadrangular

22

 

Achenes flattened, compressed or obcompressed

26

22. (21)

Leaves alternate; pappus of relatively long capillary setae

Neurolaena

 

Leaves opposite (rarely leaves alternate or whorled); pappus absent, or of short, medium or long squamellae, or of short capillary setae

23

23. (22)

Annual or short-lived perennial herbs; mature achenes roughened; anthers free

Eleutheranthera

 

Perennial herbs, subshrubs or shrubs, sometimes scandent; mature achenes smooth; anthers connate

24

24. (23)

Pappus of short, medium or long scales; disc corollas with reddish resin ducts

Calea p.p.

 

Pappus absent or of short deciduous setae; disc corollas with colourless resin ducts

25

25. (24)

Corollas white; achenes not fleshy; pappus setae deciduous of few short setae

Melanthera

 

Corollas yellow; achenes with fleshy surface; epappose

Tilesia

26. (21)

All achenes obcompressed, flattened on inner and outer surfaces; paleae flat

Coreopsis

 

Disc achenes laterally compressed; paleae conduplicate about achenes or paleae absent

27

27. (26)

Capitula lacking ray florets

28

 

Capitula radiate

31

28. (27)

Capitula with 3-5 disc florets; receptacle small, epaleaceous, not conical; achenes with internal pale striations

29

 

Capitula with 14-240 disc florets; receptacle large, obviously paleaceous, conical; achenes lacking pale striations in phytomelanin layer

30

29. (28)

Achenes with prominent basal elaiosome, body wingless and short-setuliferous throughout; pappus a fringe of short scales

Garcilassa

 

Achene lacking elaiosome, body wings lacerate to crenellate, setuliferous only towards apex; pappus of 2 short, thick hispid awns

Synedrellopsis

30. (28)

Shrubs or vines; inflorescence thyrsoid with corymbose branches

Salmea

 

Perennial herbs; inflorescences or solitary long-pedicellate capitula

Spilanthes

31. (27)

Achenes winged

32

 

Achenes usually terete or angled but lacking wings

33

32. (31)

Involucre with distinct outer series of foliaceous bracts; body of achene not constricted into neck; style arms strongly coiled

Dimerostemma

 

Involucre lacking outer foliaceous bracts; body of achene constricted above into neck; style arms recurved

Oyedaea

33. (31)

Inner phyllaries broadly rounded; leaves opposite; achenes lacking pale striations in phytomelanin layer; sick style arms with two separate stigmatic lines

34

 

Inner phyllaries narrow, acute; leaves often alternate; achenes with pale striations in phytomelanin layer; disk style arms with one continuous stigmatic surface on inside or each

35

34. (33)

Achenes with narrow bases, lacking elaiosome; Pappus a short laciniate crown, lacking neck at apex of achene

Elaphandra

 

Achenes with broad bases, with small or large elaiosome; pappus of squamellae fused into short crown above a short neck with 1-3 awns (rarely awns absent)

Aspilia

35. (33)

Pedicel inflated and fistulose beneath involucre

Tithonia

 

Pedicel not inflated or fistulose beneath involucre

36

36. (35)

Style arms of disk florets with long slender apical appendages

Simsia

 

Style arms lacking apical appendage or with only short appendages

37

37. (36)

Pappus awns easily deciduous

Pappobolus

 

Pappus awns persistent or achenes epappose

38

38. (37)

Basal secondary veins of leaf strongly divergent from basal leaf margins; style arms apices with projecting appendage; ray florets 6-11

Hymenostephium

 

Basal secondary veins subparallel with and close to basal margins of lamina; style arm apices with out appendage, with or without projecting cell tips; ray florets 14-32

Viguiera

39. (19)

Capitula with 1 or 2 rays asymmetrically arranged

40

 

Capitula with 3 or more radially arranged rays

41

40. (39)

Capitula with few to many florets enclosed in radially symmetrical involucre; both radiate and discoid capitula present in inflorescence, and if radiate with only 1 or 2 ray florets; achenes 10-ribbed, somewhat flattened

Flaveria

 

Capitula obcompressed, with 2 or 5 florets enclosed in zygomorphic involucre of 1 or 2 greatly enlarged round phyllaries; all capitula radiate; achenes triquetrous

Delilia

41. (39)

Receptacles epaleaceous

42

 

Receptacles paleaceous, paleae broad or filiform

44

42. (41)

Achenes epappose

Villanova

 

Achenes pappose

43

43. (42)

Phyllary margins membranaceous; involucre obovate or obtrullate in outline; pedicel not enlarged beneath involucre; style arms acute

Schkuhria

 

Phyllary margins herbaceous; involucre campanulate or hemispherical; pedicel enlarged beneath involucre; style arms truncate

Hymenoxys

44. (41)

Achenes of ray florets with marginal wing with many deep narrow lobes

Synedrella

 

Achenes of ray florets without many-lobed wings, usually wingless

45

45. (44)

Ray florets with large, persistent corollas on achenes (i.e. abscission zone absent)

46

 

Ray florets with small corollas or deciduous

48

46. (45)

Phyllaries gradate; disc florets functionally male

Zinnia

 

Phyllaries subequal in length; disc florets hermaphrodite

47

47. (46)

Ray achenes with pappus of few teeth or a minute rim; capitula distinctly pedicellate, pedicels inflated beneath involucre; ray corollas with tube

Heliopsis

 

Ray achenes with pappus of 3 stout spine-like awns and one broader awn; capitula sessile; ray corollas without tube

Sanvitalia

48. (45)

Disk achenes laterally compressed, sometimes with marginal wings

49

 

Disk achenes terete or prismatic, often quadrangular

55

49. (48)

Achenes constricted beneath pappus or with short neck or beak

50

 

Achenes not constricted beneath pappus, or slightly narrower beneath pappus

51

50. (49)

Plants mainly prostrate; capitula solitary on erect pedicels; achenes without distinct carpopodium or elaiosomes at base, beak and pappus obscured at maturity by corky collar, body conspicuously tuberculate

Sphagneticola

 

Plants mostly erect or shrubby; capitula rarely solitary; achenes with distinct carpopodium and elaiosomes at base; beak and pappus not obscured at maturity by corky collar, body smooth or only slightly tuberculate

Wedelia

51. (49)

Receptacle markedly conical or columnar

Acmella

 

Receptacle flat or convex to only slightly conical

52

52. (51)

Scrambling shrubs or vines; branches short, squarrose

Oblivia

 

Erect herbs or subshrubs; branches not squarrose

53

53. (52)

Achenes dimorphic (ray achenes somewhat clavate and unwinged, disc achenes compressed and prominently winged); pappus absent; style arms with penicillate appendages as long as or much longer than stgmatic area

Chrysanthellum

 

Achenes monomorphic; pappus of 2 apical awns; style arm appendages shorter than stigmatic area

54

54. (53)

Corollas mostly deep purple or yellowish-purple, sometimes pink; achenes wingless; leaves more or less rosulate and basal; rootstock xylopodiaceous or tuberous

Isostigma

 

Corollas yellow white or orange; achenes broadly winged; leaves often cauline; rootstock fibrous or with distinct taproot

Verbesina

55. (48)

Achenes epappose

56

 

Achenes with pappus setae or awns or scales

59

56. (55)

Outer phyllaries spreading and with many stipitate glands

Siegesbeckia

 

Outer phyllaries not spreading and eglandular

57

57. (56)

Capitula sessile at anthesis but elongating after; small turf plants of high elevations

Aphanactis

 

Pedicels not elongating after anthesis

58

58. (57)

Paleae filiform; phyllaries not equal in number to ray florets and not conduplicate about ray achenes; receptacle slightly convex; achenes tuberculate

Eclipta

 

Paleae broad; phyllaries equal in number to ray florets and partially conduplicate about ray achenes; receptacle conical; achenes smooth

Jaegeria

59. (55)

Pappus of many long barbellate or plumose setae

60

 

Pappus of awns or scales

61

60. (59)

Pappus of barbellate capillary setae, somewhat deciduous; inflorescence a very many-headed corymbose-panicle

Schistocarpha

 

Pappus of plumose setae, persistent; inflorescence scapiform or a few-headed cymose-panicle

Tridax

61. (59)

Ray corollas yellow; ray achenes and disk achenes with similar pappus

Calea p.p.

 

Ray corollas whitish or purplish; ray achenes with reduced pappus or pappus absent

Galinsoga