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Stigonema
(of photobionts): a genus of filamentous cyanobacteria having “true branching”,
resulting from perpendicular divisions of cells within the filament, found only in few
cyanobacterial lichens (e.g. in
Ephebe
).
Stipitate
(of apothecia)
:
brought on a peduncle
.
Sub-
(general suffix): partially, incompletely, approaching (e.g.
submuriform
), or “lying under
something else” (e.g.
subhymenium
).
Subhymenium
(of apothecia): in the strict sense, this is the part of the
apothecium
(visible in
microscopic sections) which corresponds to the generative tissue below the
hymenium
. In
our keys, it is most often used as a synonym of
hypothecium
.
Submuriform
(of spores): weakly
muriform
, with a few longitudinal septa only.
Sulcate
(of thallus parts): furrowed, e.g. the surface of
Parmelia sulcata
.
Taxon
(plural: taxa): any unit in a classification scheme (family, genus, species, subspecies,
etc.).
Terete
(of thallus, or thallus parts): round in cross-section (e.g. the branches of many
Usnea
-
species).
Terricolous
(of lichens): growing on soil.
Tetrachotomous
(of thallus parts): 4-branched (e.g. in some species of
Cladonia
).
Thalline
(of apothecial margins): the margin of
lecanorine apothecia
, produced by the thallus
and hence containing the
photobionts
. Usually, the thalline margin has the same colour of
the thallus, and differs in colour from the
disc
(e.g. in
Lecanora chlarotera
). Sometimes,
however, especially when the thallus is similar in colour to the disc (e.g. in some species of
Candelariella
and
Caloplaca
), a section is needed to reveal the photobiont in the margin.
Thalloconidia
(singular: thalloconidium): structures serving to the vegetative reproduction of
the mycobiont. They are very small and rounded, and consist of small clumps of hyphae,
which are produced on the thallus, on the
prothallus
. Rare, and limited to genera such as
Umbilicaria
(from the lower cortex), and
Protoparmelia
(e.g.
P. leproloma
, from the margin
of areolae).
Thalline
(of apothecial margin): see
margin
.
Thalloconidia
: small propagules for the vegetative dispersal of the
mycobiont
, formed directly
on the
thallus
. They may be confused with
soredia
, which, however, contain some cells of
the
photobiont
, while the thallonoconidia are formed only by the mycobiont.
Thallus
(plural: thalli): the “body” of the lichen, formed by the myco- and the photobiont,
excluding the parts devoted to sexual reproduction of the
mycobiont
(
ascocarps
)
.
Thecium
(of ascocarps): a synonym of
hymenium
. The parts lying above and under the
hymenium are often called
epihymenium
and
subhymenium
. The latter term, however, is
rather ambiguous. The term
thecium
is never used in our keys, but we consistently call its
upper and lower parts
epithecium
and
hypothecium
.
Tholus
(of asci):
the apex of
bitunicate asci
, when the two walls become distant from each
other, giving the impression of an apical thickening.
Its features, best observed after
application of
J
, are important for distinguishing among supraspecific ranks. They were
rarely used in our keys, being often difficult to appreciate, but are mentioned in the
descriptions.
Tomentose
(of thallus):
having a cover of soft, matted
hairs
, best seen under a binocular
microscope or a strong lens.
Torus
(of spores): a thickening occurring near the septum of pluricellular spores, e.g. in
Rinodina
.
Trentepohlioid
(of photobiont): a green alga related to
Trentepohlia
. The algal layer has a
characteristic orange to greenish orange colour.
Trichotomous
(of thallus parts): 3-branched, e.g. the thallus of
Cladonia portentosa
.
Truncate
(of thallus parts): ending abruptly, e.g. the
lobes
of
Parmelia sulcata
.
