37
appears in the form of thin, branched bundles of hyphae exploring the substratum. See also
hypothallus
.
Pruina
: powdery, frost-like deposits of crystals (often calcium oxalates), present on the
cortex
,
or on the
ascocarps
; they may be very small and powdery, or aggregated into larger clumps;
they are usually white, rarely of other colours (e.g. yellow in some
Caliciales
).
Pruinose
: covered by
pruina
.
Pseudo-
(general suffix): resembling to something without being it (e.g.
Pseudopodetia
).
Pseudocyphellae
(singular: pseudocyphella): small interruptions of the
cortex
where the
medulla
is exposed to facilitate gas exchange. They may be linear-elongate (e.g. in
Parmelia
sulcata
), reticulate (e.g. in
Parmotrema reticulatum
), punctiform (e.g. in
Punctelia
subrudecta
). This character is important, esp. for foliose lichens, but is often difficult to
appreciate for beginners (cracks in the cortex are often mistaken for pseudocyphellae).
Pseudopodetia
(singular: pseudopodetium): in the dictionary of Fungi this term is defined as
follows “
a lichenised, podetium-like structure of vegetative origin, ascogonia arising on this
not on the pre-formed granular or squamulose thallus initials
”. The difference between
podetia and pseudopodetia has to do with their ontogeny (see
primary
), and lies outside the
scope of our identification keys. In the dichotomies, pseudopodetia are mostly subsumed
under
podetia
.
Pubescent
(of thallus parts): covered by thin, short hairs.
Pustula
(plural: pustulae): bubble-like swellings present on the thalli of some species (e.g.
Collema nigrescens
,
Lasallia
).
Pustulate
(of thallus): covered by
pustula
e
.
Pycnidia
(singular: pycnidium): flask-like structures, resembling
perithecia
, in which
spermogonia
are produced. They are mostly, but not always, dark-coloured, immersed in the
thallus, appearing as small dots. Sometimes, however, they become prominent (e.g. in some
Micarea
species), and may have very different colours (from white to yellow-orange).
Pycnidiospores
: see
spermatia
. This term is never used in our keys.
Pyrenium
(of perithecia): the
wall
of
perithecia
. A term which is never used in our keys. See
also
excipulum
.
Pyrenocarpic
(of mycobionts): lichenised fungi with
perithecia
.
Pyrenolichen
: a lichen with
perithecia
.
Pyriform
(of spores, perithecia): pear-shaped.
Reniform
(of spores): kidney-like, curved.
Reticulate
: net-like and interconnected (e.g. like the pseudocyphellae of
Parmotrema
reticulatum
).
Revolute
(of thallus parts): bent downward.
Rhizines
: bundles of hyphae mostly originating from the lower
cortex
, which anchor
foliose
or
squamulose
lichens to the substratum. Their shape and length may be important diagnostic
characters in some genera (e.g.
Peltigera
). See also
rhizohyphae
.
Rhizohyphae
: individual hyphae, pigmented or colourless, which anchor the squamules of
some lichens (e.g.
Catapyrenium
s.lat.) to the substratum. They should be not confused with
rhizines
, which originate from the lower
cortex
, and are stouter, being composed of thick
bundles of
hyphae
.
Rimose
(of thallus): irregularly and minutely cracked, without distinct
areolae
. A rather odd
term, which is seldom used in our keys.
Rosette-shaped
(of thallus): rounded in shape, symmetrical, mostly with radiating marginal
lobes
(e.g.
Squamarina lentigera
).
Saddle-shaped
(of apothecia): used only for some
Peltigera-
species, those whose apothecia are
elongated and curved, like the saddle of a horse (e.g.
P. polydactyla
), as opposed to those
with flattened, horizontal apothecia (e.g.
P. horizontalis
).
