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This key is prepared by Ted Ahti and Harrie Sipman for a scheduled volume on Cladoniaceae in the Flora of the Guianas. It is a preliminary version, which contains some unpublished names, scheduled for publication in a forthcoming volume of Flora Neotropica or in the Flora of the Guianas. Comments and remarks are very welcome. Please contact Included are all Cladoniaceae known from the three Guianas and from the rest of the Guyana Highland. Therefore the key can be used also for collections from the Venezuelan and Brazilian parts of this area.

1a   Primary thallus squamulose to foliose; podetia
     squamulose or not                                     Cladonia
1b   Primary thallus absent or crustose; podetia or
     pseudopodetia never squamulose                        2

2a   Cortex well developed, cartilaginous, measuring
     about half of the podetial wall; podetium surface
     smooth, shiny, with numerous rounded to elliptic
     lateral perforations; central canal surrounded by an
     arachnoid medulla, its surface felty                  Cladia
2b   Cortex thin or absent; podetium surface smooth or
     minutely felty, dull or slightly shiny, rarely with
     lateral perforations; central canal surrounded by a
     usually cartilagineous layer of conglutinated hyphae
     occupying about half of the width of the podetial
     wall (stereome), its surface smooth to slightly
     papillose, rarely granular or felty                   3

3a   Podetia richly branched, greenish-yellow to ash-
     grey, without scyphi, cortex, soredia, granules or
     squamules                                             Cladina
3b   Podetia unbranched to moderately (rarely very
     densely) branched, greenish-yellow, brown or grey,
     often with scyphi, usually with a cortex, sometimes
     with soredia or granules, often squamulose, at least
     in young stagesor on basal parts                      Cladonia


1a   Forming semiglobose heads; branching type extremely
     dense, isotomic, without distinct main axes           C. globosa
1b   Forming flattened mats; branching type looser,
     mainly anisotomic, with distinct main axes            C. aggregata


1a   Usnic acid present; colour greenish to yellowish
     grey                                                  2
1b   No usnic acid; colour grey                            4

2a   P+ & K+ intensely yellow (thamnolic or stictic acid)
     or P- & K- (barbatic or squamatic acids); surface
     smooth, corticoid                                     11 - Cladonia key
2b   P+ orange red & K- (fumarprotocetraric acid) or P-
     & K- (perlatolic acid); surface clearly felty, not
     corticoid                                             3

3a   P- (perlatolic acid); forming broad, dense,
     semiglobose heads; trichotomic branchings often
     frequent; no main axis distinguishable                C. confusa
3b   P+ red (fumarprotocetraric acid); trichotomic
     branchings always rare; a main axis in part
     distinguishable                                       C. densissima

4a   P+ intensely yellow (thamnolic acid) or P- (barbatic
     or squamatic acid; if perlatolic acid, see couplet
     3)                                                    21 - Cladonia key
4b   P+ orange red (fumarprotocetraric acid)               5

5a   Podetia near the tips with thick and compact felt
     layer, with smooth surface without protruding algal
     cell clusters and without visible stereome surface;
     main axes always clearly distinct except near the
     tips; tips often deflexed                             6
5b   Podetia near the tips with thin and arachnoid felt
     layer, with rugulose surface caused by protruding
     algal cell clusters and with often visible stereome
     surface; main axes present or absent; tips spreading
     to deflexed                                           8

6a   Apical branchlets blunt with very thick felt layer;
     mostly over 0.5 mm wide at 1 mm below the tips;
     colour whitish to pale grey                           C. argentea
6b   Apical branchlets subulate with thinner felt layer;
     under 0.5 mm wide at 1 mm below the tips; colour
     pale grey, often with a brownish to violet tinge      7

7a   Apical branchlets with mostly short (c. 0.1 mm long)
     brownish points; without discoloured branchlets near
     the tips; colour pale grey to whitish grey; common
     at lower to mid elevations                            C. sprucei
7b   Apical branchlets with long (c. 0.2-0.5 mm) brownish
     points; often with browned branchlets near the tips;
     colour bluish- to violet- or brownish grey; rare
     high-altitude species                                 C. rangiferina
                                                           subsp. abbayesii

8a   Stereome strongly blackening at base; top branchlets
     also blackening, slender, dichotomous, deflexed;
     anisotomy distinct, with distinct main axes; heads
     narrow, not semiglobose                               C. atrans
8b   Stereome and tips not or little blackening; isotomy
     pronounced but main axes sometimes distinguishable
     in basal parts; forming broad rounded, often
     semiglobose heads                                     9

9a   K- (atranorin absent, homosekikaic acid often
     present); surface largely bare; brown to greenish-
     grey; forming broad, confluent, often flattish
     colonies                                              Cladonia signata
9b   K+ yellow (atranorin present; homosekikaic acid
     absent); surface thinly felty; ashy grey; forming
     regular, rounded heads                                10

10a  Heads very dense, regularly semiglobose; main axes
     absent; stereome never blackening                     C. rotundata
10b  Heads less dense, irregularly semiglobose; main axes
     distinguishable in basal parts; stereome sometimes
     blackening at the base                                C. dendroides


1a   Mature thallus dominated by squamules; podetia also
     in adult stage (with apothecia) scarcely longer than
     the squamules                                         2
1b   Mature thallus dominated by podetia, which exceed
     the squamules in length many times, or squamules
     absent                                                10

2a   Podetia present, beset with fragile or dehiscent,
     recurved squamules; rarely with apothecia, which are
     brown; P+ red (fumarprotocetraric acid)               3
2b   Podetia absent or present, then not with fragile or
     dehiscent squamules, but often with red apothecia;
     P- or P+ yellow (when P+ red, see 2a)                 4

3a   Podetial squamules rounded; sterile podetia obtuse,
     occasionally very narrowly scyphose; basal squamules
     without marginal fibrils                              C. pityrophylla
3b   Podetial squamules narrowly elongate, often almost
     isidia-like; sterile podetia subulate, never
     scyphose; basal squamules usually with scattered,
     white marginal fibrils                                C. ceratophylla

4a   Squamules with marginal soredia or isidia             5
4b   Not sorediate, nor isidiate                           9

5a   Both basal and podetial squamules elongate; margins
     farinosely sorediate; medulla white                   C. meridionalis
5b   Basal squamules roundish; sometimes isidiate to
     sorediate at margins                                  6

6a   Medulla (and squamules beneath) red                   C. miniata
6b   Medulla and lower side of squamules white             7

7a   Squamules elongate, finely divided, thin (c. 0.15
     mm), P+ red                                           C. termitorum
7b   Squamules rounded, thick (c. 0.3 mm), P-              8

8a   Squamules with sorediate margins                      C. ahtii
8b   Squamules with cylindrical isidia on the margins      C. sp. A

9a   Medulla red; with rounded basal squamules; podetia
     thick, flat                                           C. miniata
9b   Medulla white; with elongate basal squamules;
     podetia thin, terete                                  C. secundana

10a  Podetia densely branched, without suamules and with
     smooth, not felty surface (NB. For densely branched
     Cladonia species without squamules and with
     tomentose, non-corticate surface see key to Cladina
     species. Some Cladina species may have a largely
     smooth surface; check near the tips of the podetia!)  11
10b  Podetia less densely branched or unbranched, or with
     squamules                                             28

11a  Thallus with yellowish tinge, containing usnic acid
11b  Thallus whitish-grey to brown, without yellowish
     tinge                                                 21

12a  Main axes for the most part over 2 mm thick and
     inflated, very strongly and irregularly branched;
     wall often split and perforated laterally; inner
     wall reticulate; P+ red, P+ pale yellow or P-
     (usually containing fumarprotocetraric acid or
     stictic acid)                                         C. subreticulata
12b  Main axes under 2 mm thick and not inflated, less
     strongly and more regularly, usually dichotomically
     branched; wall not perforated or at axils only;
     inner wall not reticulate; P+ yellow or P- (usually
     containing thamnolic, barbatic or squamatic acids)    13

13a  Central canal of podetium with glossy, smooth wall    14
13b  Central canal of podetium with matt, puberulent or
     felty wall                                            18

14a  Podetia mostly under 0.4 mm wide, without distinct
     main axes                                             C. peltastica
14b  Podetia 0.5-1 mm wide, often with main axes           15

15a  Not densely branched, forming loose tufts with
     coarse main axes; P+ yellow, K+ yellow (thamnolic
     acid)                                                 16
15b  Densely branched, forming "spiny" heads with thin,
     indistinct main axes; P-, K- (barbatic and/or
     squamatic acid), rarely P+ yellow or red, K+ yellow
     or K-                                                 17

16a  Branchlets at the ultimate tips at an obtuse angle;
     squamules absent; widespread in sandstone tableland   C. vareschii
16b  Branchlest at the ultimate tips at a sharp angle;
     squamules often present, but maybe scarce; high
     elevations only                                       C. flavocrispata

17a  Thallus P-, K- (barbatic and/or squamatic acid),
     rarely P+ yellow, K+ yellow (thamnolic acid)          C. spinea
17b  Thallus P+ red, K- (fumarprotocetraric acid)          C. chimantae

18a  Stereome absent, replaced by a compacted medullary
     layer; P+ yellow (thamnolic acid)                     C. crassiuscula
18b  Stereome present, cartilaginous; P+ yellow, K+
     yellow or P-, K-                                      19

19a  Thin, much branched, creeping to erect; surface of
     central canal somewhat fibrose; in herbarium fine
     needle crystals develop at the podetial tips; P- or +
     weakly yellow, K+ yellow, slowly turning red
     (stictic acid)                                        C. substellata
19b  Stoutish, erect, often with dominant main axes;
     surface of central canal smooth; no development of
     needle crystals at the tips; P+ yellow, K+ yellow
     (thamnolic acid), rarely P-, K- (squamatic acid)      20

20a  Podetia thick, little, and strongly anisotomically
     branched, pale greyish yellow with brown-variegated
     parts towards the base; cortex thin; stereome thin
     and soft; always P+ yellow, K+ yellow                 C. sufflata
20b  Podetia slender, moderately, more or less
     anisotomically branched, clearly yellow, uniformly
     coloured througout; cortex thick; stereome strong;
     P+ yellow, K+ yellow or P-, K-                        C. steyermarkii

21a  Branching usually clearly anisotomic, main axes
     distinct; not forming very dense, rounded heads       22
21b  Branching mostly isotomic, no main axes distinct;
     usually forming very dense, rounded to elongate
     heads                                                 25

22a  Podetia little branched, thick (to 3 mm); stereome
     soft and white; wall of central canal pruinose;
     among mosses on peat                                  C. sufflata
22b  Podetia much branched, thin (to 1 mm); stereome hard
     and hyaline; wall of central canal shiny; usually
     free-growing on sand or sandstone flats               23

23a  Branchlet tips ending in fine, blackish tips (0.5-)
     1-2 mm long and 0.1-0.2 mm wide                       C. huberi
23b  Branchlet tips pale or shorter and wider              24

24a  Podetia of uniform, grey colour; axils often closed,
     not much dilated; common in white-sand savannas near
     the coast                                             C. sipmanii
24b  Podetia variegated with whitish and brown patches,
     particularly on older parts; axils mostly perforated
     and often widely dilated and funnel-shaped; in
     sandstone tablelands of the interior                  C. hians

25a  Stereome replaced by a layer of incompletely
     conglutinated hyphae; branches not over 0.4 mm wide
     lower down in the cushions; forming rounded, but
     more or less coalescing heads                         C. pulviniformis
25b  Stereome completely conglutinated                     26

26a  Podetia 0.4-0.8 mm thick, usually variegate;
     internodes usually under 2 mm long                    C. variegata
26b  Podetia 0.2-0.4 mm thick, sometimes variegate;
     internodes usually over 2 mm long                     27

27a  Surface of the podetia completely smooth; tips
     mostly pointing upward; not variegate                 C. peltastica
27b  Surface of the podetia usually slightly felty; tips
     pointing in all directions; sometimes variegate       C. signata

28a  Podetia sorediate, granulose or verrucose to
     squamulose, largely ecorticate and felty inbetween,
     or with strongly verrucose surface                    29
28b  Podetia smooth and mainly corticate, without soredia
     or granules, sometimes with scattered squamules       42

29a  Podetia broadly scyphose (cup-shaped), scyphi (cups)
     at least three times as wide as the stalk (in well-
     developed podetia)                                    30
29b  Podetia ascyphose, or scyphose but then scyphi
     narrow, only slightly wider than the rest of the
     podetium                                              32

30a  Podetia with yellowish tinge (usnic acid, KC+
     yellow), P+ yellow; apothecia red; scyphi sorediate
     and/or granular, stalk corticate                      31
30b  Podetia not yellowish (KC-), P+ red
     (fumarprotocetraric acid); apothecia brown; scyphi
     and stalk totally sorediate                           C. subsquamosa

31a  Podetia farinose sorediate                            C. mollis
31b  Podetia not truly sorediate but smooth to coarsely
     granulose                                             C. corallifera

32a  Podetia not sorediate, simple or little branched;
     tips usually persistently subulate, sometimes with
     narrow scyphi; smooth or with deciduous small
     squamules or corticate granules, hardly truly
     sorediate                                             33
32b  Podetia sorediate, branchy or not; podetia often
     finally with narrow scyphi; with (ecorticate)
     soredia                                               39

33a  Apothecia red; P+ yellow, red or P- (for narrowly
     scyphose specimens see C. corallifera)                34
33b  Apothecia brown or absent; P+ yellow or red           35

34a  Podetia very small, up to 4 mm tall; cortex
     verruculose; on termite mounds                        C. termitorum
34b  Up to 1 cm tall; almost ecorticate, microsquamulose
     to granulose; mostly on wood                          C. didyma

35a  P+ yellow, K+ yellow (thamnolic acid); slender, with
     numerous squamules; ascyphose, but sometimes with
     scyphoid, wide open axils                             36
35b  P+ red, K- (fumarprotocetraric acid); slender to
     stout; squamulose or not; often scyphose              37

36a  Podetia slender, often with soredioid granules; with
     closed axils; mostly on bark of living trees          C. subdelicatula
36b  Podetia more robust, without soredioid granules;
     with widened, scyphoid, open axils; mostly on sand    C. polystomata

37a  Podetial squamules rounded, horizontal, often
     strongly concave or convex; podetia rarely ending in
     distinct scyphi                                       C. pityrophylla
37b  Podetial squamules elongate, down-turning, flat to
     slightly convex                                       38

38a  Podetia usually ending in small scyphi;               C. furfuraceoides
38b  Podetia without scyphi, always with subulate tips     C. corymbites

39a  Apothecia red; podetia thick and short, pale whitish
     yellow to whitish (usnic acid often present in low
     amounts), densely sorediate; corticate near base; on
     wood; P+ yellow, K+ yellow (thamnolic acid)           C. prancei
39b  Apothecia brown; podetia long subulate, grey to
     brownish (usnic acid never present), thinly
     sorediate or with granules, which may be attached to
     each other and form microsquamules; on wood or sand;
     P+ red, K- (fumarprotocetraric acid)(when P+ yellow,
     K+ yellow, see also C. subdelicatula)                 40

40a  Podetia with open axils; P+ yellow, K+ yellow         C. granulosa
40b  Podetia with closed axils; P+ red, K-                 41

41a  Podetia completely ecorticate, pale greenish
     throughout; mainly on vertical faces of wood          C. subradiata
41b  Podetia corticate near base and below scyphi, pale
     grey and easily browning, sometimes melanotic below;
     mainly on mineral soil                                C. polyscypha

42a  Podetia regularly scyphose; scyphi proliferating
     from the center                                       C. rappii
42b  Podetia subulate or bluntish, often branchy,
     occasionally with scyphoid, enlarged open axils
     (funnels), or with small scyphi proliferating from
     the margin                                            43

43a  With yellow tinge (usnic acid, sometimes in low
     concentrations)                                       44
43b  Without yellow tinge                                  45

44a  Podetia usually under 0.5 mm thick, moderately to
     densely branching, with narrowly perforated or
     closed axils; often abundant at lower elevations; P+
     yellow or P-                                          C. peltastica
44b  Podetia usually over 1 mm wide, with widely opened
     axils; rare, at high-altitide                         C. hians

45a  Apothecia red, usually present; podetia almost
     unbranched, stoutish, with strongly areolate cortex
     and somewhat squamulose                               C. guianensis
45b  Apothecia brown, rarely present; podetia branched,
     more or less squamulose                               46

46a  Podetia strongly squamulose; cortex glossy; P+
     yellow, K+ yellow (thamnolic acid) or P-, K-
     (squamatic acid) (if P+ red, K-, then see couplet
     16)                                                   C. sphacelata
46b  Podetia scarcely squamulose; cortex not glossy; P+
     yellow or red, K+ yellow or K-                        47

47a  P+ red, K- (fumarprotocetraric acid); very densely
     branched (resembling Cladina); usually forming
     large, brown mats; squamules very scarce              C. signata
47b  P+ yellow, K+ yellow (thamnolic acid) or P-, K-
     (various substances); moderately branched; squamules
     common                                                48

48a  Whitish-grey; podetia thin, 0.4-0.6 mm, erect, very
     fragile, scarcely branched and with closed axils;
     cortex often rugulose                                 C. rugulosa
48b  Ashy grey; podetia thin or stoutish, entangled and
     richly branched, not very fragile; axils more or
     less perforated                                       49

49a  Podetia thin, rarely over 0.4 mm wide, without main
     axes; axils closed                                    C. peltastica
49b  Podetia thick, with clear main axes c. 1 mm wide;
     axils often wide open                                 50

50a  Not all axils perforated, especially not near tips,
     and the perforations small; surface almost
     continuously corticate and of uniform, greyish
     colour; common in coastal white sand savanna          C. sipmanii
50b  All axils gaping open, often funnel-shaped; surface
     variegated with pale and dark patches, at least in
     older parts of the podetia; restricted to the
     sandstone tablelands                                  C. hians

by Ted Ahti and Harrie Sipman, for the Biological Diversity of the Guianas Program, 1997

Guianas Lichen Index

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