[BGBM-Logo] Lichen determination keys
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Key to foliose lichens

1a Thallus gelatinous when humid; photobiont Nostoc in chains, embedded in a gelatinous layer, rarely other gelatinous photobiont genera, with scattered cells; thallus homoiomerous, without arachnoid, alga-free medulla ---2
1b Thallus not gelatinous; photobiont green or bluegreen, when Nostoc, then in glomerules with little jelly; thallus heteromerous, with arachnoid, alga-free medulla ---6

2a Photobiont Nostoc, with cells arranged in chains ---3
2b Photobiont different, with cells arranged in small groups or separate ---5

3a Thallus without cortex; spores transversely septate to muriform ---Collema
3b Thallus without cortex; spores simple ---Staurolemma
3c Thallus with a pseudoparenchymatic cortex of one cell layer (in microscopical section) ---4

4a Spores transversely septate or muriform; thallus often under 0.5 mm thick ---Leptogium
4b Spores simple; thallus over 0.5 mm thick ---Physma

5a Thallus attached by central holdfast (umbilicus); on rock (provisionally treated group; other genera may key out here) ---Thyrea
5b Thallus attached by various spots of its lower surface; over terricolous mosses ---Omphalina

6a (1) Thallus attached by central holdfast (umbilicus); on rock ---7
6b Thallus attached not by umbilicus, but by rhizines or otherwise, attachment points spread all over the underside; on various substrates ---9

7a Thallus surface bright yellow ---Placomaronea
7b Thallus surface grey to brown or dark brown ---8

8a Perithecia present, immersed in the thallus, producing simple, hyaline ascospores ---Dermatocarpon
8b Apothecia present or no ascocarps present ---Umbilicaria

9a Thallus surface yellow to orange, K+ dark violet or K- ---10
9b Thallus surface dark brown or grey to greenish- or yellowish grey, K- or K+ yellowish ---15

10a Thallus surface yellow, K-; ascospores simple ---11
10b Thallus surface yellow to orange, K+ dark violet; ascospores polarilocular ---13

11a Thallus lobes rounded with concentric ridges; algae bluegreen ---Coccocarpia
11b Thallus lobes elongate or much divided, without concentric ridges; algae green ---12

12a Thallus lobes hardly over 1 mm wide ---Candelaria
12b Thallus lobes usually over 1 mm wide ---Pseudoparmelia

13a Ascospores bilocular ---14
13b Ascospores tetralocular ---Teloschistes

14a Upper and lower cortex paraplectenchymatic, with rounded lumina much wider than walls ---Xanthoria
14b Upper and lower cortex prosoplectenchymatic, with elongate lumina not wider than walls ---Josefpoeltia
14c Upper cortex paraplectenchymatic, lower cortex prosoplectenchymatic ---Xanthomendoza

15a (9) Lower side smooth, with cortex, with or without rhizines ---16
15b Lower side more or less tomentose, with or without cortex, with or without rhizines ---70

16a Upper surface of lobes with white, rounded or elongate pseudocyphellae ---17
16b Upper surface of lobes without pseudocyphellae ---20

17a Thallus yellowish to greenish grey, with usnic acid in the cortex ---Flavopunctelia
17b Thallus whitish grey, with atranorin in the cortex ---18

18a Pseudocyphellae elongate, more or less connected in a reticulate pattern (if pseudocyphellae producing soredia or isidia, see Parmelia) ---Pyxine
18b Pseudocyphellae rounded, without reticulate pattern ---19

19a Lobes ascending, usually over 1 cm wide; lower side black ---Cetrelia
19b Lobes appressed to substrate, under 1 cm wide; lower side often white, sometimes black ---Punctelia

20a Cilia present on the lobe margins; rhizines present or absent on lower side ---21
20b Cilia absent from the margins; rhizines present or absent on lower side ---34

21a Cilia with inflated base ---22
21b Cilia without inflated base ---23

22a Upper side of thallus yellowish green; usnic acid present ---Relicina
22b Upper side of thallus whitish grey; atranorin present ---Bulbothrix

23a Marginal rhizines or cilia white or grey, sometimes black, but then usually with perpendicular side branchlets, felty; ascospores one-septate, dark ---Heterodermia
23b Marginal rhizines or cilia black, mostly unbranched; ascospores simple, colourless ---24

24a Rhizines one or more times dichotomously branched ---Hypotrachyna
24b Rhizines unbranched, sometimes partly irregularly branched, or absent ---25

25a Thallus lobes linear, with parallel margins, more or less dichotomously branched ---26
25b Thallus lobes elongate, with irregularly bent margins, irregularly branched ---28

26a Lower side brown, without rhizines; terricolous lichen with upright lobes ---Cetraria
26b Lower side black, with or without rhizines; predominantly epiphytic with spreading lobes ---27

27a Lobes regularly dichotomously branched; apothecia concave when young ---Everniastrum
27b Lobes irregularly branched; apothecia flat to convex when young ---Cetrariastrum

28a Thallus lobes elongate, mostly under 2 mm wide, flattened ---29
28b Thallus lobes short and wide, mostly over 5 mm wide, often ascending ---31

29a Cilia robust, tapering; upper surface white-maculate ---Canomaculina
29b Cilia slender, not tapering; upper surface uniformly grey ---30

30a Medulla yellow to orange ---Myelochroa
30b Medulla white ---Parmelinopsis

31a Underside near lobe tips without rhizines, naked in a several mm wide zone ---Parmotrema
31b Underside rhizinate to the margin ---32

32a Lobe tips appressed to substratum; rhizines of uniform length, shorter towards the lobe tips ---Parmotremopsis
32b Lobe tips ascending; rhizines of variable length, often dimorphic ---33

33a Underside near margin brown, with scattered rhizines of variable length ---Rimelia
33b Underside near margin pale, with dense, short rhizines mixed with scattered longer ones ---Rimeliella

34a (20) Rhizines completely absent ---35
34b Rhizines present, frequent or scattered ---41

35a Thallus lobes hollow, with cavity between medulla and black lower cortex; above 3000 m ---36
35b Thallus lobes compact; at various elevations ---37

36a Thallus with perforations on upper side ---Menegazzia
36b Thallus without perforations on upper side ---Hypogymnia

37a Thallus lobes erect, attached only near base; lower side often white near the tips, black lower down; epiphytic ---Pseudevernia
37b Thallus appressed to substrate; lower side black; epiphytic or epilithic ---38

38a Upper side yellowish or greenish grey, with usnic acid; ascospores hyaline, simple; epilithic at high altitude ---Psiloparmelia
38b Upper side pale to dark grey, without usnic acid; ascospores grey, 1-3-septate; widespread ---39

39a Thallus K+ yellow (cortex containing atranorin); apothecia with dark hypothecium; thallus lobes elongate and laterally confluent ---Dirinaria
39b Thallus K- (cortex lacking atranorin); apothecia with pale hypothecium; thallus lobes not laterally confluent ---Hyperphyscia


41a (34) Thallus pale yellowish on both sides; lower side with pseudocyphellae; rhizines scarce ---Cetraria
41b Thallus not pale yellowish on both sides; lower side without pseudocyphellae ---42

42a Rhizines absent from a wide marginal zone, usually scarce and restricted to small patches; thallus lobes wide, often over 10 mm wide ---Parmotrema
42b Rhizines present till (close to the) lobe margins, regularly spread all over the surface; thallus lobes usually up to 2 mm wide, rather narrow and deeply dissected ---43

43a Rhizines frequently dichotomously branched ---Hypotrachyna
43b Rhizines mostly unbranched or a few times irregularly branched ---44

44a Apothecia completely black, without grey thalline margin when well developed ---Pyxine
44b Apothecia with grey thalline margin ---45

45a Ascospores one-septate, grey to brown; thallus closely appressed to the substrate (except Heterodermia with pale lower side); lower side whitish or black ---46
45b Ascospores simple, hyaline; thallus mostly loosely appressed to the substrate; lower side brown to black ---49

46a Thallus more or less ascendant; cortex prosoplectenchymatic, composed of longitudinally arranged hyphae; upper surface faintly longitudinally striate ---Heterodermia
46b Thallus flattened; cortex paraplectenchymatic, or prosoplectenchymatic but then hyphae not longitudinally arranged; upper surface not striate ---47

47a Apothecia with dark hypothecium; thallus closely applicated to substrate, with adjoined lobes almost forming a crust, usually with divaricatic acid, difficult to separate from substrate and lower side thus difficult to observe ---Dirinaria
47b Apothecia with pale hypothecium; thallus less closely applicated to substrate and clearly foliose, without divaricatic acid, more easily separable from substrate and therefore lower side easily observable ---48

48a Upper surface pale grey, K+ yellow; medulla always white ---Physcia
48b Upper surface dark grey, K-negative; medulla sometimes orange-red ---Phaeophyscia

49a Thallus upper surface whitish grey, with atranorin, usually without usnic acid ---50
49b Thallus upper surface yellowish- to greenish grey, with usnic acid, without atranorin ---53

50a Lower surface pale brown to brown; ascospores less than 10 µm long ---51
50b Lower surface dark brown to black; ascospores over 10 µm long ---52

51a Thallus closely appressed to rock ---Paraparmelia
51b Thallus loosely appressed to bark, rarely on rock ---Pseudoparmelia

52a Pycnoconidia more or less bifusiform, to c. 8 µm long; below 3000 m ---Canoparmelia
52b Pycnoconidia curved, 10-20 µm long; above 3000 m ---Parmeliopsis

53a Thallus lobes with rounded tips, over 2 mm wide, flat to concave; epiphytic or on mossy rock ---Flavoparmelia
53b Thallus lobes with slightly incised tips, often under 2 mm wide, flat to convex; saxicolous or terricolous ---Xanthoparmelia

70a (15) Lobes with tomentose or felty lower side, at least partly so; veins, rhizines or cilia sometimes present ---71
70b Lobes with naked, smooth lower side; veins and rhizines absent, cilia occasionally present ---83

71a Thallus linear, with thick tomentose layer throughout on underside ---Anzia
71b Thallus irregularly lobed, with thin or interrupted tomentose layer on underside, at least near the margins, or with felty lower side ---72

72a Thalli with usually large, over 5 mm wide lobes, mostly ascending or loosely appressed; algae blue-green or green ---73
72b Thalli with small, rarely over 5 mm wide, lobes, usually closely appressed; algae always blue-green; apothecia ---76

73a Small, white to yellow points without tomentum present on lower side (cyphellae or pseudocyphellae) ---74
73b Lower side continuously tomentose, or with larger and vaguely delimited patches without tomentum (cyphellae or pseudocyphellae absent) ---75

74a Cyphellae present: white spots on lower side with prominent, raised margin ---Sticta
74b Pseudocyphellae present: yellow spots on lower side without raised margin ---Pseudocyphellaria

75a Thallus with larger, not sharply delimited, pale, tomentum-free areas on lower side; veins absent; maculae or pseudocyphellae absent from upper side; usually epiphytic ---Lobaria
75b Like a; maculae or pseudocyphellae present on upper side ---Lobariella
75c Thallus continuously tomentose on lowerside; wider or narrower, vein-like, raised bands on lower side present; usually on soil ---Peltigera

76a Upper surface tomentose; tomentum on lower side often restricted to marginal patches; uncommon ---Erioderma
76b Upper surface glabrous; tomentum on lower side usually spread over most of the thallus ---77

77a Lower side veined with glabrous veins and felty interspaces ---Solorina
77b Lower side with tomentum usually spread over most of the thallus ---78

78a Cortex composed of longitudinally arranged hyphae; thallus often with concentric ridges; apothecia without thalline margin ---Coccocarpia
78b Cortex not composed of longitudinally arranged hyphae; thallus without concentric ridges; apothecia often with thalline margin ---79

79a Thallus closely appressed to substrate, almost crustose; lobes usually to 1(-2) mm wide ---80
79b Thallus loosely appressed with ascending margins, distinctly foliose; lobes usually over 2 mm wide ---82

80a Ascospores over 100 per ascus; photobiont cells in tetrads or single ---Phyllopeltula
80b Ascospores 8 per ascus; photobiont cells in densely winding chains ---81

81a Thallus without distinct prothallus; apothecia always with thalline margin ---Pannaria
81b Thallus with distinct, often tomentose, prothallus; apothecia with or without thalline margin ---Parmeliella

82a Apothecia on upper surface, often absent ---Leioderma
82b Apothecia on lower side, at the tips of lobules, usually present ---Nephroma

83a (70) Thallus scarcely dissected, lobes ± hemispherical; basidiolichen, without ascocarps ---Dictyonema
83b Thallus strongly dissected, lobes usually much longer than wide; ascolichen, apothecia often present ---84

84a Epiphytic or among moss; cilia present ---Heterodermia
84b Terricolous at high elevations; cilia absent ---85

85a Lobes wide, c. 5 mm; apothecia immersed in the lobes, brown ---Solorina
85b Lobes narrow, c. 1 mm; apothecia stalked, pink ---Phyllobaeis

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page editor: Harrie Sipman, last update: 17 October 2005, imprint