Family key to Group 2

Group 2: Aquatic pls in vegetative condition; sporangia, sporangium cases, seeds, cones, or cone-like structures 0 or not readily apparent

1. Plant body consisting of a jointed, hollow-stemmed central axis and whorled branches; leaves reduced to whorled scales; plant emergent ..... EQUISETACEAE {G3}

1' Plant body various, but not consisting of a jointed, hollow-stemmed central axis and whorled branches; leaves various, but not whorled scales; plant free-floating, emergent, or submersed

2. Plant raft-like, free-floating on water surface or stranded along shore or in drying bottom sediments, breaking apart into individuals or small clumps

3. Individual plant generally 0.4–30 mm in length or diam, sometimes not differentiated into leaves and stems; roots unbranched

4. Plant body spheric to disk-shaped or oblong, not differentiated into stems and leaves ..... ARACEAE (3) {G6,8,13,15}

4' Plant body differentiated into a short, often branched stem with small, minutely velvety-papillate, scale-like leaves ..... AZOLLACEAE {G3}

3' Individual plant often >> 30 mm, differentiated into leaves and stems; roots generally branched (0 in Salviniaceae, with finely dissected, root-like submersed leaves)

5. Lf blades glossy green, glabrous, finely parallel-veined; petioles often enlarged, forming gas-filled floats ..... PONTEDERIACEAE (Eichhornia)

5' Lf blades light to dark green or ± purple, velvety-hairy, ± palmately or obscurely veined, sessile, lacking floats, ± palmately or obscurely veined

6. Lvs in floating rosettes, evidently ± palmately veined ..... ARACEAE ([Pistia]) {G15}

6' Lvs in whorls of 3, 2 floating, entire, obscurely veined, the 3rd submersed, finely dissected, root-like ..... SALVINIACEAE {G3}

2' Plant generally anchored in bottom sediments or, if free-floating, most of plant body below water surface or not readily breaking apart — rhizomes or stolons present or 0, sometimes elongated

7. Lf peltate, cordate, sagittate, or deeply notched

8. Lf peltate

9. Submersed parts not gelatinous; leaf blades generally emergent ..... ARALIACEAE (Hydrocotyle) (2) {G14,21}

9' Submersed parts gelatinous; leaf blades floating ..... CABOMBACEAE (Brasenia)

8' Lf sagittate or cordate to ovate or ± round, the base shallowly to deeply notched

10. Lf blades pinnately veined; petioles long, stout; rhizome stout

11. Lf sagittate; rhizome ± vertical ..... ARACEAE ([Peltandra]) (2)

11' Lf ovate to round; rhizome horizontal ..... NYMPHAEACEAE

10' Lf blades ± palmately veined; petioles long or short, slender or stout; rhizome, if present, slender

12. Lf blades palmately lobed, never sagittate, the lobes often toothed — veinlets forming an irregular network ..... ARALIACEAE (Hydrocotyle) (2) {G14,21}

12' Lf blades ovate to cordate or sagittate, entire

13. Palmate veins 3 — smaller veins parallel, extending from main veins toward leaf margin ..... ARACEAE ([Peltandra]) (2)

13' Palmate veins generally 5–13+

14. Stipules 1–6 cm ..... PONTEDERIACEAE (Heteranthera limosa) (3)

14' Stipules 0

15. Smaller veins passing like ladder-rungs between prominent main veins ..... ALISMATACEAE or

15' Smaller veins forming network ..... MENYANTHACEAE (Nymphoides) {G19}

7' Lf not peltate, cordate, sagittate, or deeply notched

16. Lvs all basal or basal and cauline on a generally erect, generally emergent stem, sometimes from rhizome or corm-like base anchored in bottom sediments

17. Lvs petioled, with expanded blades

18. Lf serrate or dentate to lobed or compound

19. Lf palmate; leaflets 4 ..... MARSILEACEAE (Marsilea) (2) {G3}

19' Lf toothed to pinnately lobed or 1–3-pinnate

20. Lf bases sheathing; leaves, lobes, or leaflets serrate to sharply dissected ..... APIACEAE (2) {G6,8,14,20,21}

20' Lf bases not sheathing; lobes or leaflets entire or dentate with ± rounded teeth ..... BRASSICACEAE (Nasturtium, Rorippa)

18' Lf entire, simple

21. Lvs generally << 1 cm wide ..... SCROPHULARIACEAE (Limosella) (2) {G18,19}

21' Lvs generally >= 1 cm wide, often much larger

22. Wider leaves floating ..... APONOGETONACEAE {G10}

22' Wider leaves generally emergent

23. Stipules 0 ..... ALISMATACEAE (2) {G10}

23' Stipules present, 1–6 cm ..... PONTEDERIACEAE (Heteranthera limosa) (3)

17' Lvs sessile, ± linear or reduced to bladeless sheaths

24. Lvs vertically folded and attached "edge-on" to the stem, obviously 2-ranked ..... JUNCACEAE (Juncus) (4)

24' Lvs cylindric, ± angled, flat, or reduced to bladeless sheaths, but not folded, not obviously 2-ranked

25. Lvs with flat blades or reduced to bladeless sheaths

26. Lvs bladeless or nearly so, composed mainly of a tubular sheath

27. Sts ± triangular ..... CYPERACEAE (4) {G8,13}

27' Sts round, flattened, or several-angled

28. Lf sheaths closed, forming a continuous cylinder around stem ..... CYPERACEAE (4) {G8,13}

28' Lf sheaths open on one side, with overlapping margins ..... JUNCACEAE (Juncus) (4)

26' Lvs with ordinary flat blades and generally also ± tubular sheaths

29. Lf blade with a well-developed midvein or keel

30. Lf sheaths closed, forming a continuous cylinder around stem; stem generally triangular; leaves 3-ranked ..... CYPERACEAE (4) {G8,13}

30' Lf sheaths open on one side, with overlapping margins; stem round; leaves 2-ranked ..... TYPHACEAE (Sparganium) (3) {G6,8,13}

29' Lf blade flat or rounded on back, lacking a prominent midvein or keel

31. Annual; leaves all basal ..... RANUNCULACEAE (Myosurus)

31' Perennial, or if annual, some leaves cauline

32. Plant submersed; seawater or brackish water of bays and estuaries ..... ZOSTERACEAE (2) {G6,8,13}

32' Plant emergent; fresh or brackish water of coastal or inland areas

33. Nodes swollen; stem generally hollow ..... POACEAE (2) {G5,6,8,13}

33' Nodes not swollen; stem generally filled to center with spongy tissue

34. Lf generally > 5 mm wide; remnants of old inflorescence a dense spike; inner surface of leaf sheaths mucilaginous ..... TYPHACEAE (Typha)

34' Lf <= 5 mm wide; remnants of old inflorescence not evident or a raceme; inner surface of sheaths not mucilaginous

35. Lvs ± circular to semicircular in ×-section ..... JUNCAGINACEAE (3) {G10,13,16}

35' Lvs flat ..... PONTEDERIACEAE (Heteranthera limosa) (3)

25' Lvs cylindric or angled

36. Rhizomes and stolons 0; leaves densely tufted

37. Lf divided lengthwise into 4 hollow chambers; a sporangium generally embedded in adaxial base of each leaf, containing either powdery or larger spores ..... ISOETACEAE {G3}

37' Lf solid or hollow, but not regularly divided into 4 chambers; a sporangium never embedded in leaf base

38. Plant per; leaf often with internal cross-partitions ..... JUNCACEAE (Juncus) (4)

38' Plant annual; leaf without internal cross-partitions or partitions obscure

39. Lf bases not sheathing ..... BRASSICACEAE (Subularia)

39' Lf bases sheathing ..... JUNCAGINACEAE (3) {G10,13,16}

36' Rhizomes or stolons present; leaves tufted or borne along rhizome or stolon

40. Lf sharply angled

41. St triangular; leaves 3-ranked ..... CYPERACEAE (4) {G8,13}

41' St ± round; leaves 2-ranked ..... TYPHACEAE (Sparganium) (3) {G6,8,13}

40' Lf cylindric

42. Lf with internal cross-partitions

43. Lf soft, blunt, generally <= 15 cm, loosely sheathing; cross-partitions often externally prominent ..... APIACEAE (Lilaeopsis)

43' Lf generally stiff, acute, often > 15 cm, tightly sheathing; cross-partitions readily apparent by feel but often externally obscure ..... JUNCACEAE (Juncus) (4)

42' Lf without internal cross-partitions

44. Lf generally >> 6 cm

45. St ± straight; leaf blade tip without evident terminal pore; ligule 0.5–5 mm ..... JUNCAGINACEAE (3) {G10,13,16}

45' St zigzag; leaf blade tip with evident terminal pore; ligule 2–12 mm ..... SCHEUCHZERIACEAE {G10}

44' Lf 1–7(11) cm

46. Plant spreading by rhizomes, producing ± spheric, ball-like structures [sporangium cases] ± 2–3 mm diam at bases of some leaves; new leaves uncoiling at tips ..... MARSILEACEAE (Pilularia) {G3}

46' Plant spreading by stolons, not producing ball-like structures at bases of leaves; new leaves not uncoiling at tips ..... SCROPHULARIACEAE (Limosella) (2) {G18,19}

16' Lvs generally all cauline; stems emergent or taking the form of underwater or floating rhizomes or stolons that are unable to support the plant body outside of water

47. Lvs (or leaf-like branches) compound or very deeply divided

48. Lf palmately compound — leaflets 4, floating or emergent ..... MARSILEACEAE (Marsilea) (2) {G3}

48' Lf pinnately compound or variously dissected

49. Lflets lanceolate or wider; leaves mostly aerial

50. Lf bases sheathing; lobes or leaflets serrate to sharply dissected ..... APIACEAE (2) {G6,8,14,20,21}

50' Lf bases not sheathing; lobes or leaflets entire or dentate with ± rounded teeth ..... BRASSICACEAE (Nasturtium, Rorippa)

49' Lflets or lobes linear, at least on submersed leaves; all or many leaves submersed

51. Underwater parts bearing small, hollow bladders that suck in and trap small organisms when hairs at opening are triggered; plant carnivorous — highly dissected underwater parts are actually modified stems and the bladders are the leaves ..... LENTIBULARIACEAE (Utricularia) {G18}

51' Underwater parts lacking bladder-like traps; plant not carnivorous

52. Submersed leaves alternate ..... RANUNCULACEAE (Ranunculus) (3)

52' Submersed leaves opposite or whorled

53. Submersed leaves pinnately divided, central leaf axis evident ..... HALORAGACEAE {G6,8,14,20}

53' Submersed leaves palmately dissected or repeatedly forked, central leaf axis 0

54. Submersed leaves palmately dissected; floating leaves 0–few, linear-elliptic, ± entire ..... CABOMBACEAE (Cabomba)

54' Submersed leaves repeatedly forked; floating leaves 0 ..... CERATOPHYLLACEAE {G6,8,14,15}

47' Lvs simple, the margins entire, toothed, or shallowly lobed

55. Lvs long, narrow, strap-shaped or ribbon-like, often >> 20 cm, generally at least some basal

56. Plant of freshwater habitat ..... TYPHACEAE (Sparganium) (3) {G6,8,13}

56' Plant of seawater or brackish water of bays and estuaries ..... ZOSTERACEAE (2) {G6,8,13}

55' Lvs linear to round, generally < 20 cm, generally all cauline

57. Lf with stipules or sheathing base

58. Principal veins of leaf pinnate

59. Lvs opposite or whorled, 2–15 mm ..... ELATINACEAE

59' Lvs alternate, >> 15 mm ..... POLYGONACEAE {G6,8,15,16,19}

58' Principal veins of leaf parallel or pinnate-parallel or only 1 leaf vein apparent

60. Lvs generally ± opposite or appearing whorled

61. Lvs emergent or floating; nodes swollen, internodes generally hollow ..... POACEAE (2) {G5,6,8,13}

61' Lvs submersed or some floating; nodes generally not swollen, internodes generally solid

62. Lvs minutely toothed (teeth sometimes appearing ± 0 to naked eye); leaf base abruptly expanded, forming sheath, stipules 0 ..... HYDROCHARITACEAE (Najas) {G8,13}

62' Lvs entire; leaf base not abruptly expanded, stipules present, free or fused to leaf base forming a sheath ..... ZANNICHELLIACEAE {G8,10,13}

60' Lvs generally alternate

63. Stipules ± completely fused to leaf blade base ..... RUPPIACEAE {G8,10,13}

63' Stipules fused to leaf blade base <= 2/3 their length

64. Roots branched; leaves linear; midvein of leaf not differentiated from other veins; floating leaves 0 ..... PONTEDERIACEAE (Heteranthera dubia)

64' Roots generally unbranched; leaves linear to ovate; midvein of leaf more prominent than other veins; floating leaves often present ..... POTAMOGETONACEAE {G10,13}

57' Lf without stipules or sheathing base

65. Lvs alternate

66. Lvs sessile; annual ..... CAMPANULACEAE {G5,14,17}

66' Lvs petioled; perennial herb

67. Lvs toothed or lobed ..... RANUNCULACEAE (Ranunculus) (3)

67' Lvs entire

68. Lateral leaf veins strongly diverging from midvein ..... ONAGRACEAE (Ludwigia) (2)

68' Lateral leaf veins strongly ascending to nearly parallel to midvein ..... RANUNCULACEAE (Ranunculus) (3)

65' Lvs opposite or whorled

69. Lvs whorled

70. Lf minutely toothed (teeth sometimes appearing ± 0 to naked eye) ..... HYDROCHARITACEAE (2) {G6,8,16}

70' Lf entire ..... PLANTAGINACEAE (Hippuris) {G14,15}

69' Lvs opposite

71. Lvs fleshy

72. Lvs 2–6 mm, linear or oblanceolate; annual; plant generally ± red ..... CRASSULACEAE (Crassula aquatica)

72' Lvs 3–50 mm linear to obovate; annual or perennial herb; plant generally not red ..... MONTIACEAE (Montia) {G5}

71' Lvs not or scarcely fleshy

73. Lvs 0.5–5 mm wide

74. Lvs minutely toothed (teeth sometimes appearing ± 0 to naked eye) to coarsely dentate, generally enlarged at base, all similar in form and submersed ..... HYDROCHARITACEAE (2) {G6,8,16}

74' Lvs entire, linear to ovate, not enlarged at base, sometimes with floating distal leaves different from submersed leaves ..... PLANTAGINACEAE (Callitriche) {G8,15}

73' Lvs 6–15+ mm wide

75. Lf veins palmate ..... PHRYMACEAE or

75' Lf veins pinnate

76. Lvs toothed ..... PHRYMACEAE or

76' Lvs entire

77. Lvs (3)5–13 cm; stems often swollen, hollow ..... AMARANTHACEAE (Alternanthera)

77' Lvs < 5 cm; stems not swollen ..... ONAGRACEAE (Ludwigia) or PLANTAGINACEAE (Veronica) (2)