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1a - Thallus placodioid, effigurate to almost foliose .......................................................................... 2
1b - Thallus crustose, not effigurate or almost foliose ........................................................................ 6

2a - Thallus grayish white to yellowish brown, lacking usnic acid, containing xanthones,
        strictly maritime ....................................................................................................................... 3
2b - Thallus greenish to yellowish, containing usnic acid, not especially maritime ......................... 4

3a - Thallus consisting of scattered lobate areoles, not rosette-forming; infrequent ..........
        ...................................................................................................................... L. contractula Nyl.
3b - Thallus forming rosettes, with very narrow, parallel, peripheral lobes; known only from
        the type ......................................................................................................... L. microbola Lamb

4a - Apothecial discs pruinose, pale or brown, rare ............................................... L. weberi Ryan
4b - Apothecial discs epruinose, greenish or orange-yellow ......................................................... 5

5a - Thallus with narrow lobes, often paler or blackish at the edges; containing zeorin, lacking
        placodiolic acid ................................................................ L. muralis (Schreb.) Norman
5b - Thallus with dispersed, loosely attached, lobate areoles, uniform in color, often resembling
        a Rhizoplaca species, lacking zeorin, containing placodiolic acid ........ L. opiniconensis Brodo

6a - Thallus growing on siliceous rocks ........................................................................................ 7
6b - Thallus growing on other substrates ...................................................................................... 23

7a - Thallus sorediate ................................................................................................................... 8
7b - Thallus not sorediate ............................................................................................................. 9

8a - Thallus gray (lacking usnic acid), with discrete soralia, lacking a prothallus;
         rare ........................................................................................................... L. umbrosa Degel.
8b - Thallus yellowish green (containing usnic acid), leprose, with a white fibrous
         prothallus; common ..................................................................... L. thysanophora R.C. Harris

9a - Thallus K + yellow, containing atranorin, whitish, grayish, or yellowish green ................... 10
9b - Thallus K -, lacking atranorin, whitish or yellowish-green to green ..................................... 19

10a - Apothecial discs heavily pruinose, C + orange, containing chromones ............................. 11
10b - Apothecial discs epruinose or slightly pruinose ................................................................ 12

11a - Apothecia constricted at base to slightly stalked, discs bluish pruinose, with parathecial
          crown .................................................................................................... L. bicincta Ramond
11b - Apothecia sessile to immersed, discs whitish or grayish pruinose, lacking parathecial
          crown ................................................................................................ L. rupicola (L.) Zahlbr.

12a - Apothecia aspicilioid or biatorine (not lecanorine), black; epihymenium blue-green,
          HNO₃+ deep red ........................................................................................................ 13
12b - Apothecia lecanorine, brown to almost black; epihymenium reddish brown (HNO₃-)
          to olive (HNO₃+ pinkish) .....................................................................,,................... 14

13a- Apothecia biatorine, thallus containing usnic acid; alpine ................................
        ....................................................................... L. marginata (Schaerer) Hertel & Rambold
13b - Apothecia aspicilioid, thallus lacking usnic acid; low elevations ...................
        .......................................................................... L. oreinoides (Körber) Hertel & Rambold

14a - Amphithecium containing small crystals; strictly maritime ................ L. xylophila Hue
14b - Amphithecium containing large crystals; mostly not maritime ...................................... 15

15a - Epihymenium red-brown to olive, with abundant crystals (POL+), crystals in epipsamma
         and pigmentation dissolving in KOH ............................................................. L. cenisia Ach.
15b - Epihymenium red-brown or dark brown to blackish, lacking crystals (POL-) or with very
         few crystals, pigmentation remaining in KOH or changing color ....................................... 16

16a - Apothecial discs dark brown to blackish, epihymenium often changing to greenish in KOH,
          with few crystals on surface ........... L. argentea Oxner & Volkova (syn. L. fuliginosa Brodo)
16b - Apothecial discs red-brown to dark brown, epihymenium red-brown, lacking crystals,
          not altered in KOH ............................................................................................................. 17

17a - Thallus continuous to rimose-areolate, containing zeorin ................. L. subimmergens Vain.
17b - Thallus granular-verrucose or dispersed areolate, not continuous to rimose ...................... 18

18a - Thallus dispersed areolate, spores 5.5-7 µm wide, containing 2'-O-methylperlatolic acid,
           lacking zeorin ........................................................................................... L. pseudistera Nyl.
18b - Thallus granular-verrucose, spores 7-9 µm wide, lacking 2'-O-methylperlatolic acid,
           containing zeorin ...................................................................................... L. perplexa Brodo

19a - Thallus whitish to grayish, C+ orange, containing xanthones, lacking usnic acid and zeorin,
        apothecia red-brown; maritime .................................................................... L. contractula Nyl.
19b - Thallus yellowish to greenish, C-, lacking xanthones, containing usnic acid and zeorin,
          apothecia yellowish green, yellowish brown or greenish brown, not red-brown; not
          maritime .............................................................................................................................. 20

20a - Thallus thick, with convex areoles; apothecial discs pale to dark yellowish brown,
          epruinose, usually with a conspicuous parathecial crown (inner ring)....L.chlorophaeodes Nyl.
              (The placodioid L. weberi ,with pruinose discs, is similar; see 4a)
20b - Thallus thick, thin, or endolithic; areoles, if present, not thick and convex; apothecial discs
          yellowish brown to greenish brown, lacking a conspicuous parathecial crown ................... 21

21a - Apothecia immersed in thallus, apothecial disc greenish brown ; thallus well-developed,
        continuous to areolate ............................................................................. L. intricata (Ach.) Ach.
21b - Apothecia sessile, apothecial disc yellowish-green .............................................................. 22

22a - Ascospores broadly ellipsoid to ellipsoid, 5-6 µm wide, apothecia lecanorine; thallus scanty,
          dispersed areolate to entirely endolithic; common .................... L. polytropa (Hoffm.) Rabenh.
22b - Ascospores narrowly ellpsoid, 3-4 µm wide, apothecia biatorine; thallus dispersed to
          continuous areolate; rare ............................................................ L. ochraceorubescens Arnold

23a - On calciferous rocks ............................................................................................................... 24
23b - On bark, soil or mosses .......................................................................................................... 26

24a - Thallus whitish, well developed .................... L. albescens (Hoffm.) Branth & Rostrup
24b - Thallus thin, almost invisible or reduced to small parts surrounding apothecia ...................... 25

25a - Apothecial margins thick, crenulate, often discontinuous ........................... L. crenulata Hook.
25b - Apothecial margin thin or thick, not crenulate or discontinuous ..........................................
             ......................................................................................... L. dispersa (Pers. ) Sommerf. s. lat.

26a - On soil or mosses ................................................................................................................... 27
26b - On bark or wood .................................................................................................................... 28

27a - Apothecial margin K- (lacking atranorin); amphithecium lacking crystals, [containing
          5,7-dichlorolichexanthone or lacking secondary metabolites] ................ L. hagenii (Ach.) Ach.
27b - Apothecial margin K+ yellow (containing atranorin); amphithecium with small
         crystals ................................................................................................. L. epibryon (Ach.) Ach.

28a - Thallus or apothecial margins yellowish to greenish, containing usnic or isousnic acids ......  29
28b - Thallus or apothecial margins whitish, grayish or brownish, lacking usnic acid ................... 39

29a - Thallus or apothecial margins sorediate ................................................................................. 30
29b - Thallus and apothecial margins esorediate ............................................................................. 34

30a - Thallus thin, with conspicuous, white, fibrous prothallus ...... L. thysanophora R.C. Harris ined.
30b - Thallus thin or thick, prothallus not visible or inconspicuous ................................................ 31

31a - Thallus esorediate, apothecial margins granular-sorediate ........ L. strobilina (Sprengel) Kieffer
31b - Thallus and apothecial margins sorediate ............................................................................... 32

32a - Thallus C-, P+ orange-red, containing fumarprotocetraric acid, soralia greenish-gray .......
           ........................................................................................... L. conizaeoides Nyl. ex Crombie
32b - Thallus C+ orange, P-, containing xanthones ......................................................................... 33

33a - Soralia bluish gray, well delimited, on wood near seashores ............ L. orae-frigidae R. Sant.
33b - Soralia yellowish green, soon covering whole thallus, on wood or bark near
          seashores ....................................................................................................... L. expallens Ach.

34a - Apothecial margins biatorine, soon becoming excluded ......................................................... 35
34b - Apothecial margins biatorine or lecanorine, persistent .......................................................... 36

35a - Ascospores 9-16 x 4-5.5 µm, apothecial discs bright yellow, pale yellow-green or
          yellow-brown, thallus thin or verruculose, yellowish gray or whitish, epiphloeodal ..........
                 .................................................. L. symmicta (Ach.) Ach. s.lat. (syn. L. symmictera Nyl.)
35b - Ascospores 5.5-10 (-12) x 2.5-4.5 (-5) µm, apothecial discs waxy yellow-brown to
          yellow-green or olive-brown to brownish black, thallus inconspicuous, greenish or
          yellowish-green, usually endophloeodal ..................................... L. subintricata (Nyl.) Th. Fr.

36a - Apothecia biatorine .......................................................................... L. symmicta (Ach.) Ach.
36b - Apothecia lecanorine ............................................................................................................ 37

37a - Apothecial discs with a bright yellow pruina, margins thick, crenulate; contains usnic
          acid .............................................................................................................. L. cupressi Tuck.
37b - Apothecial discs greenish, gray- or pink-brown or yellowish, without yellow pruina; margins
          thin; contains isousnic acid .................................................................................................. 38

38a - Apothecial margin smooth, level with the disk; spores narrowly ellipsoid, 7-14 x3-4.1 µm
           .............................................................................................................. L. piniperda Körber
38b - Apothecial margin thalline in texture, usually prominent; spores ellipsoid to broadlyellipsoid,
         7-13 x 4-7 µm ............................................................................... L. saligna (Schrader) Zahlbr.

39a - Thallus K+ distinctly yellow, containing atranorin .............................................................. 40
39b - Thallus K-, lacking atranorin ............................................................................................... 59

40a - Apothecial discs heavily whitish pruinose; apothecial sections P+ red-orange .........,......... 41
40b - Apothecial discs epruinose or slightly pruinose; apothecial sections P- or PD+ red ........... 43

41a - Apothecia 0.3-1.5 mm in diam., apothecial margins thin, pseudocortex 35-75 µm thick;
          contains protocetraric acid .................................................................... L. albella (Pers.) Ach.
41b - Apothecia 0.8-3.0 mm in diam., apothecial margins thick, pseudocortex 45-105 µm thick;
          contains virensic or protocetraric acid ........... "L. caesiorubella" Ach.:  .......................... 42

42a - Apothecial disks C+ yellow, margin (in section) K+ red (norstictic acid); contains
          protocetraric acid; coastal plain ................................. subsp. prolifera (Fink) R.C. Harris
42b - Apothecial disks C-, margin (in section) K+ yellow (lacking norstictic acid); contains
          virensic acid; boreal-montane ............................................................ subsp. caesiorubella

43a - Thallus sorediate .................................................................................................................. 44
43b - Thallus esorediate ................................................................................................................ 45

44a - Amphithecium with large crystals, thallus dark grayish yellow, on wood;
          rare ............................................................................................................. L. farinaria Borrer
44b - Amphithecium with small crystals, thallus whitish, on bark; common ........ L. impudens Degel.

45a - Amphithecium with small crystals, epihymenium egranulose ............................................... 46
45b - Amphithecium with large crystals, epihymenium granulose or egranulose ........................... 49

46a - Amphithecial cortex absent or indistinct .................................................. L. imshaugii Brodo
46b - Amphithecial cortex present, gelatinous ............................................................................... 47

47a - Amphithecial cortex distinctly delimited, small crystals confined to medulla, on driftwood
          at seashore ........................................................ L. xylophila Hue (syn. L. grantii H. Magn.)
47b - Amphithecial cortex indistinctly delimited, small crystals in medulla extending into cortex,
          usually on bark .................................................................................................................... 48

48a - Apothecia large, (0.5-)0.7-2.0(-3.0) mm in diameter, constricted at base, ascospores
          13-18 x 7-11 µm .......................................................................................L. allophana Nyl.
48b - Apothecia small, 0.3-.6(-1.2) mm in diameter, adnate, ascospores 9-13 x 6-8 µm .........
            ............................................................................................... L. glabrata (Ach.) Malme

49a - Epihymenium egranulose, pigmentation not dissolving in KOH, but sometimes
          altering color ...................................................................................................................... 50
49b - Epihymenium granulose, crystals and pigmentation dissolving in KOH .............................. 51

50a - Amphithecial cortex distinct, thallus verrucose to continuous, contains gangaleoidin,
          lacks zeorin .............................................L. argentata (Ach.) Malme [includes L. subrugosa]
50b - Amphithecial cortex thin, indistinct, thallus granulose-verrucose, lacks gangaleoidin,
          contains zeorin .............................................................................. L. perplexa Brodo

51a - Epihymenium inspersed with fine granules, granules insoluble in HNO₃  ............................ 52
51b - Epihymenium with coarse granules at surface, granules soluble in HNO₃ ........................... 54

52a - Amphithecial cortex basally expanded, ascospores 12-18 x 8-11 µm, apothecial disc usually
          pitch black to dark brown ................................................... L. circumborealis Brodo & Vitik.
52b - Amphithecial cortex uniform or expanded, ascospores 10-14 x 6-9 µm, apothecial disc
          variable, pale to dark brown, rarely black .............................................................................. 53

53a - Usually on conifers, lignum, willows or elder, apothecial disc dark brown to red-brown,
          margin thin, amphithecial cortex thicker (2-3x) at base, thallus mostly P+ red, rarely all or
          partly P- ............................................................................................ L. pulicaris (Pers.) Ach.
53b - On deciduous trees, apothecial disc orange-brown to red-brown, margin thick, amphithecial
          cortex relatively uniform in thickness, thallus P-, very common .... L. hybocarpa (Tuck.) Brodo

54a - Amphithecial cortex very thin and inconspicuous up to 15 µm thick, epihymenium P+ orange,
          apothecia semi-immersed, at least when young .................................. L. cinereofusca H. Magn.
54b - Amphithecial cortex more than 15 µm thick, gelatinous, epihymenium P-, apothecia sessile .... 55

55a - Apothecial disks C+ orange (xanthone), dull or lightly pruinose, margins thin;coastal plain
          (Long Island, NY) ................................................................................... L. louisianae de Lesd.
55b - Apothecial disks C-, pruinose or not; margins thick or thin; common ..................................... 56

56a - Apothecia appressed, flat, broad (up to 3 mm in diam.), margins thin, discs epruinose .........
            ..................................................................................................... L. wisconsinensis H. Magn.
56b – Apothecia not appressed, small or broad, margins relatively thick, discs slightly pruinose
          or epruinose ....................................................................................................................... 57

57a - Apothecial discs dark brown to brown-black, on lignum ................................... L. cenisia Ach.
57b - Apothecial discs orange-brown to red-brown, on bark ........................................................... 58

58a - Apothecial margins smooth to slightly verrucose, thallus smooth to verruculose .........
                .......................................................................................................... L. chlarotera Nyl.
58b - Apothecial margins verrucose, thallus coarsely verrucose to granulose ........ L. rugosella Zahlbr.

59a - Asci 12-32-spored ................................................................................. L. sambuci (Pers.) Nyl.
59b - Asci 8-spored ........................................................................................................................ 60

60a - Epihymenium not granular; ascospores 10-15 x 3.5-5.3 µm ............... L. hypoptoides (Nyl.) Nyl.
60b - Epihymenium granular ............................................................................................................ 61

61a - Ascospores 6-8 x (2-) 3-3.5 (-4.5) µm, on wood, pine bark and cones ..............L. minutella Nyl.
                  (syn. L. fuscidula Degel.)
61b - Ascospores generally longer than 7 µm ................................................................................... 62

62a - Apothecial margin soon disappearing; amphithecial medulla containing few algaeconfined
          to base; ascopores ellipsoid, 6.5-10 (-12) x 3.5-5 µm ................ L. subintricata (Nyl.) Th. Fr.
62b - Apothecial margin persistent; amphithecial medulla containing abundant algae; ascospores
         (7-) 8-16 µm long ................................................................................................................. 63

63a - Apothecial margin level with disk, colored like the disk or paler, smooth; cortex usually
          indistinct or absent; ascospores narrowly ellipsoid to cylindrical, 2.5-4.1 µm wide ..........
            ......................................................................................L. piniperda Körber (var. nigrescens)
63b - Apothecial margin usually prominent, thalline in color and texture, clearly lecanorine;
          cortex well developed, gelatinous; ascospores ellipsoid, (3-) 4-7 µm wide .................
            ................................................................................................ L. hagenii (Ach.) Ach. complex
 

About this webpage:

Written by: H Thorsten Lumbsch and Irwin M. Brodo
Edited for the internet by: Philip F. May
Original date online:  16 May 2000

Comments on content to: lumbsch@uni-essen.de
Comments HTML and web-related matters: pfmay@aol.com

Suggested citation: Lumbsch, H.T. and Brodo, I.M. 2000.  Preliminary key to Lecanora species likely to occur in New England [online].  Farlow Herbarium, Harvard University, Cambridge, Massachusetts.  Available:  http://herbaria.harvard.edu/Data/Farlow/lichens/Lecanora_New_England.html