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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 It is a preliminary version, which contains some unpublished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 h.sipman
bgbm.org. 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
12
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