Plants (Key 1)

1. Stems elongated and aerial - 2

1. Stems short and corm-like - 29

1. Stems floating on water - Water Fern (Azolla filiculoides) (Lamarck, 1783)

1. Stems aerial and trunk-like - 35

1. Stems elongated and subterranean - 37

2. Stems not jointed and ridged - 3

2. Stem jointed and ridged - 13

3. Ligule absent - 4

3. Ligule present - 12

4. Stems erect - 5

4. Stems procumbent - 6

5. Stems to 30 cm, 6 - 12 mm thick - Fir Clubmoss (Huperzia selago) (Linnaeus, 1753)

5. Stems to 10 cm, 5 - 6 mm thick - Northern Clubmoss (Huperzia appressa) (Desvaux, 1827)

6. Stems arising in fan-like groups - 7

6. Stems not arising in fan-like groups - 9

7. Lateral and dorsal leaves +/- same width - Cypress Clubmoss (Lycopodium tristachyum) (Pursh, 1813)

7. Lateral leaves distinctly wider than dorsal leaves - 8

8. Ventral leaves petiolate - Alpine Clubmoss (Lycopodium alpinum) (Linnaeus, 1753)

8. Ventral leaves sessile - Issler’s Clubmoss (Lycopodium x issleri) (Rouy, 1914)

9. Lateral stems fertile only - Marsh Clubmoss (Lycopodiella inundata) (Linnaeus, 1753)

9. Lateral stems both fertile and sterile - 10

10. Leaves without a long whitish apical point - Interrupted Clubmoss (Lycopodium annotinum) (Linnaeus, 1753)

10. Leaves with a long whitish apical point - 11

11. Peduncles 2.5 - 7 cm - Stag’s-horn Clubmoss (Lycopodium clavatum) (Linnaeus, 1753)

11. Peduncles 0 - 1.2 cm - Hare’s-foot Clubmoss (Lycopodium lagopus) (Kuzeneva, 1953)

12. Branches not dorsiventrally flattened - Lesser Clubmoss (Selaginella selaginoides) (Linnaeus, 1753)

12. Branches dorsiventrally flattened - Krauss’ Clubmoss (Selaginella kraussiana) (Kunze, 1844)

13. Stems brown or whitish - 14

13. Stems green - 16

14. Leaf-sheaths with 20 - 30 teeth - Great Horsetail (Equisetum telmateia) (Ehrhart, 1783)

14. Leaf-sheaths with 3 - 20 teeth - 15

15. Leaf-sheaths with teeth united into 3 - 6 obtuse lobes at least at some nodes - Wood Horsetail (Equisetum sylvaticum) (Linnaeus, 1753)

15. Leaf-sheaths with 6 - 20 separate acute teeth - 16

16. Base of stem and leaf-sheaths usually tinged green - Shady Horsetail (Equisetum pratense) (Ehrhart, 1784)

16. Green colour absent from stem and leaf-sheaths - Field Horsetail (Equisetum arvense) (Linnaeus, 1753)

17. Usually at least some stems at least partly perennial with previous year’s cones persisting - 18

17. Stems annual - 23

18. Spores spherical and full of contents - 19

18. Spores misshapen and devoid of contents - 21

19. Leaf-sheaths with a distinct black band at distal edge - Rough Horsetail (Equisetum hyemale) (Linnaeus, 1753)

19. Leaf-sheaths without distinct black band - 20

20. Stems usually with numerous side-branches - Branched Horsetail (Equisetum ramosissimum) (Desfontaines, 1799)

20. Stems usually unbranched - Variegated Horsetail (Equisetum variegatum) (Weber and Mohr, 1807)

21. Abaxial surface of teeth of leaf-sheaths with minute prickle-like projections - Mackay’s Horsetail (Equisetum x trachyodon) (Braun 1839)

21. Abaxial surface of teeth of leaf-sheaths without prickle-like projections - 22

22. Stems usually <50 cm - Southern Horsetail (Equisetum x meridionale) (Milde, 1862)

22. Usually some stems >50 cm - Moore’s Horsetail (Equisetum x moorei) (Newman, 1854)

23. Stem internodes white - Great Horsetail (Equisetum telmateia) (Ehrhart, 1783)

23. Stem internodes green - 24

24. Branches regularly branched again - Wood Horsetail (Equisetum sylvaticum) (Linnaeus, 1753)

24. Branches absent or not regularly branched again - 25

25. Stem-internodes with central hollow >3/4 as wide as stem - Water Horsetail (Equisetum fluviatile) (Linnaeus, 1753)

25. Stem-internodes with central hollow <3/4 as wide as stem - 26

26. Stem with peripheral hollows c. same size as central hollow - Marsh Horsetail (Equisetum palustre) (Linnaeus, 1753)

26. Stem with peripheral hollows <1/2 size of central hollow - 27

27. Internodes of branches mostly 3-angled - Shady Horsetail (Equisetum pratense) (Ehrhart, 1784)

27. Internodes of branches mostly 4-angled - 28

28. Stem-internodes with central hollow c.1/2 as wide as stem - Shore Horsetail (Equisetum x litorale) (Ruprecht, 1845)

28. Stem-internodes with central hollow <1/2 as wide as stem - Field Horsetail (Equisetum arvense) (Linnaeus, 1753)

29. Leaves subulate with air cavities - 30

29. Leaves not like this - 32

30. Leaf-bases dark - Land Quillwort (Isoetes histrix) (Bory, 1846)

30. Leaf-bases not dark - 31

31. Megaspores with blunt, anastomosing tubercles on outer face - Lake Quillwort (Isoetes lacustris) (Linnaeus, 1753)

31. Megaspores with acute spines on all faces - Spring Quillwort (Isoetes echinospora) (Durieu, 1861)

32. Sterile blade simple - 33

32. Sterile blade pinnate - 34

33. Sterile blade rarely >2 cm - Least Adder’s-tongue (Ophioglossum lusitanicum) (Linnaeus, 1753)

33. Sterile blade mostly 3 - 3.5 cm - Small Adder’s-tongue (Ophioglossum azaoricum) (Presl, 1845)

33. Sterile blade mostly 4 - 15 cm - Common Adder’s-tongue (Ophioglossum vulgatum) (Linnaeus, 1753)

34. Sterile blade 1-pinnate - Common Moonwort (Botrychium lunaria) (Linnaeus, 1753)

34. Sterile blade 2-pinnate - Branched Moonwort (Botrychium matricariifolium) (Retzius, 1779)

35. Trunk scaly - Scaly Tree-fern (Alsophila tricolor) (Colenso, 1883)

35. Trunk bristly but not scaly - 36

36. Leaves up to 2 m long - Australian Tree-fern (Dicksonia antarctica) (Labillardiere, 1806)

36. Leaves up to 1.2 m long - New Zealand Tree Fern (Dicksonia fibrosa) (Colenso, 1845)

37. Leaves sterile below and fertile above - Royal Fern (Osmunda regalis) (Linnaeus, 1753)

37. Leaves either entirely sterile or entirely fertile - 38

38. Leaves very thin - 39

38. Leaves not very thin - 41

39. Petiole not winged - 39

39. Petiole winged, at least distally - Killarney Fern (Trichomanes speciosum) (Willdenow, 1810)

40. Indusium valves conspicuously dentate - Tunbridge Filmy-fern (Hymenophyllum tunbrigense) (Linnaeus, 1753)

40. Indusium valves entire - Wilson’s Filmy-fern (Hymenophyllum wilsonii) (Hooker, 1830)

41. Sterile leaves filiform, fertile leaves globose - Pillwort (Pilularia globulifera) (Linnaeus, 1753)

41. Leaves not like this - 42

42. Leaves with strong stem-like petiole - 43

42. Leaves without strong stem-like petiole - 45

43. Sori continuous around pinnule margins - 44

43. Sori in discrete groups - Pig-fern (Hypolepis ambigua) (Richard, 1832)

44. >1 main pair of pinnae - Common Bracken (Pteridium aquilinum) (Linnaeus, 1753)

44. 1 main pair of pinnae - Pine Bracken (Pteridium pinetorum) (Page and Mill, 1994)

45. Sterile and fertile leaves different - 46

45. Sterile and fertile leaves +/- similar - 47

46. Sori oblong - Parsley Fern (Cryptogramma crispa) (Linnaeus, 1753)

46. Sori linear - Jersey Fern (Anogramma leptophylla) (Linnaeus, 1753)

46. Sori +/- round - Marsh Fern (Thelypteris palustris) (Schott, 1834)

47. Sori suborbicular or round - 48

47. Sori oblong to linear - 49

48. Sori suborbicular at tips of pinnules - Southern Maidenhair-fern (Adiantum capillus-veneris) (Linnaeus, 1753)

48. Sori horseshoe-shaped around pinnule notches - Raddi’s Maidenhair-fern (Adiantum raddianum) (Presl, 1836)

48. Sori near pinnule margins - 53

48. Sori scattered on pinnule undersides - 55

49. Rhachis not winged - 50

49. Rhachis winged - Spider Brake (Pteris multifida) (Poiret, 1804)

50. Leaves not covered in scales underneath - 51

50. Leaves covered in scales underneath - Rustyback (Asplenium ceterach) (Linnaeus, 1753)

51. Indusium absent - 52

51. Indusium present - 60

52. Pinnae cuneate at base - Ribbon Fern (Pteris cretica) (Linnaeus, 1767)

52. Pinnae cordate at base - Chinese Brake (Pteris vittata) (Linnaeus, 1753)

53. Blade non-glandular - 54

53. Blade with small glands - Limestone Fern (Gymnocarpium robertianum) (Hoffmann, 1796)

54. Leaves 3-pinnate, at least at the base - Oak Fern (Gymnocarpium dryopteris) (Linnaeus, 1753)

54. Leaves 2-pinnate or 1-pinnate with the pinnae deeply lobed - Beech Fern (Phegopteris connectilis) (Michaux, 1803)

55. Leaves triangular-ovate - Mountain Bladder-fern (Cystopteris montana) (Lamarck, 1779)

55. Leaves narrowly oblong to lanceolate - 56

56. Spores rugose - Dickie’s Bladder-fern (Cystopteris dickieana) (Sim, 1848)

56. Spores spiny - 57

57. Ultimate leaf segments narrowly oblong to linear, mostly <2 mm wide - Alpine Bladder-fern (Cystopteris alpina) (Lamarck, 1779)

57. Ultimate leaf segments ovate to oblong, mostly >2 mm wide - 57

58. Most or all veins ending in pinnule-tooth apices - 59

58. Most or all veins ending in notches between pinnule-tooth apices - Diaphanous Bladder-fern (Cystopteris diaphana) (Bory, 1804)

59. Leaves without glandular hairs - Brittle Bladder-fern (Cystopteris fragilis subsp. fragilis) (Linnaeus, 1753)

59. Leaves with glandular hairs - Brittle Bladder-fern (Cystopteris fragilis subsp. huteri) (Milde, 1867)

60. Leaves simple, not lobed or lobed <1/2 way to midrib - Hart's-tongue (Asplenium scolopendrium) (Linnaeus, 1753)

60. Leaves compound, or simple and lobed >1/2 way to midrib - 61

61. Leaves with terminal portion only lobed, not pinnate - 62

61. Leaves pinnate +/- to apex - 64

62. Pinnae in lower part of blade with conspicuous gaps between - Confluent Spleenwort (Asplenium x lawalreei) (Viane, 2021)

62. Pinnae in lower part of blade without or with very small gaps between, often overlapping - 62

63. Longest pinna 2 - 8 from bottom - Moore's Spleenwort (Asplenium x microdon) (Moore, 1855)

63. Longest pinna the lowest or next to lowest - Jackson's Spleenwort (Asplenium x jacksonii) (Alston, 1940)

64. Leaves irregularly and sparsely divided into linear segments - Forked Spleenwort (Asplenium septentrionale) (Linnaeus, 1753)

64. Leaves 1-pinnate - 65

64. Leaves 2-3-pinnate - 68

65. Distal part of rhachis conspicuously green-winged - Sea Spleenwort (Asplenium marinum) (Linnaeus, 1753)

65. Rhachis not or scarcely winged - 66

66. Rhachis blackish - 67

66. Rhachis green - Green Spleenwort (Asplenium viride) (Hudson, 1762)

67. Pinnae oblong-triangular - Lobed Maidenhair Spleenwort (Asplenium csikii) (Kümmerle and Andrásovszky, 1922)

67. Pinnae suborbicular to rhombic - Small-leaved Maidenhair Spleenwort (Asplenium trichomanes) (Linnaeus, 1753)

67. Pinnae oblong - Common Maidenhair Spleenwort (Asplenium quadrivalens) (Meyer, 1962)

68. Longest pinnae at middle of blade - 69

68. Longest pinnae clearly the basal ones - 70

69. Pinnules ovate to suborbicular - Lanceolate Spleenwort (Asplenium obovatum) (Viviani, 1824)

69. Pinnules narrowly ovate to triangular - Fountain Spleenwort (Asplenium fontanum) (Linnaeus, 1753)

70. Petioles green - Wall-rue (Asplenium ruta-muraria) (Linnaeus, 1753)

70. Petioles reddish-brown to blackish - 71

71. Blade and pinnae acute to very shortly acuminate - 72

71. Blade and pinnae very long-acuminate - Irish Spleenwort (Asplenium onopteris) (Linnaeus, 1753)

72. Pinnules narrow and pointed - Black Spleenwort (Asplenium adiantum-nigrum subsp. adiantum-nigrum) (Linnaeus, 1753)

72. Pinnules wide and blunt - Black Spleenwort (Asplenium adiantum-nigrum subsp. corunnense) (Christ, 1904)