38
Scabrose
(of thallus surface): having a minutely roughened surface, generally caused by an
accumulation of dead cortical material (e.g.
Peltigera scabrosa
).
Schizidia
(singular: schizidium): structures for the vegetative reproduction of the lichen,
deriving from the scale-like flaking of the upper cortex into flattened to convex
areolae
which are detached from the thallus. They have the same function as
isidia
and
phyllidia
,
but
they are
corticate
only above (e.g.
Cladonia pyxidata
,
Fulgensia subbracteata
).
Scytonema
(of photobionts): a genus of filamentous cyanobacteria that branches by breaking
through its gelatinous sheath.
Secundary
(of thallus): see
primary
.
Semi-
(suffix): half, almost, e.g. semi-immersed = half immersed, almost immersed.
Sessile
(of apothecia)
:
sitting on the thallus, more or less constricted at the base, never stalked.
Septa
(of spores, singular: septum): cross-walls separating the individual cells of more than 1-
celled spores; their thickness is an important character in some groups (e.g. in
Caloplaca
).
Sessile
(of apothecia): not immersed, sitting on the surface, but without a stalk of any kind. See
also
stipitate
.
Soralia
(singular: soralium): well-delimited parts of thallus where
soredia
are produced
breaking the upper
cortex
. They may be of different forms:
punctiform
,
maculiform
,
labriform
,
linear
,
capitate
,
helmet-shaped
, etc.
Soredia
(singular: soredium): bundles of hyphae entwining a few
photobiont
cells, which serve
to the vegetative reproduction of the lichen. They mostly originate from the
medulla
, and
appear as powdery or granular masses. See also
blastidia
,
soralia
.
Spermogonia
(singular: spermogonium)
:
fragments of fungal hyphae produced in great number
within
pycnidia
. They may serve for vegetative reproduction (in which case they are best
called
conidia
), but their most probable role is that of acting as “male” cells for the sexual
reproduction of the
mycobiont
of ascomycetes. Their dubious role is the reason of a
confusing terminology: they are often called
conidia
,
pycnoconidia
,
pycnospores
(an odd
term, which should not be endorsed:
spores
being the product of sexual reproduction). They
may be one- or more-celled, and of very different forms and sizes. They are important in
systematics, but they rarely appear in the dichotomies of our keys, because they are not
always easy to observe. In some groups (e.g.
Micarea
) there are different types of
spermogonia, whose different functions still await elucidation: see
macroconidia
,
microconidia
.
Spores
: this term is the origin of much confusion in Mycology; it should be best used - as in our
keys - exclusively for the sexual propagules of the mycobionts, which, in the majority of
lichens, are produced inside the
asci
. Spore characters (size, shape, number of cells,
pigmentation, etc.) are important for identification. To appreciate all of them, one has to use
a professional microscope.
Squamulose
(of thallus): consisting of small, scale-like lobes lifting from the surface, at least at
the edges. Among the traditionally recognised growth-forms, this is the most ambiguous.
Typically squamulose is the primary thallus of most
Cladonia
-species, which consists of
small, leaf-like units attached to the substratum only laterally, without rhizines or other
attachment organs. However, the term is often used - also in our keys - also for and small-
fruticose thalli (e.g.
Toninia opuntioides
). Due to the bad definition of the term, the
distinction from crustose and subfruticose forms is often difficult to appreciate (e.g. in
Catapyrenium
s.str.). In our opinion, squamulose thalli in the strict sense - like foliose ones -
should have both an upper and lower surface for gas-exchange, but should be attached to the
substratum only laterally, without rhizines. In our keys we still stick to the old-fashioned,
rather vague, traditional definition of the term.
Squarrose
(of rhizinae): densely ramified, brush-like, with short, stiff perpendicular branches,
having the appearance of a bottlebrush (e.g. in
Peltigera canina
).
