Placynthium stenophyllum (Tuck.) Fink var. isidiatum Henssen
Canadian J. Bot., 41: 1706, 1963.
Synonyms:
Distribution:
Description: Thallus crustose-placodioid to subfoliose, loosely attached, medium brown, usually epruinose, isidiate, up to 230 µm thick, irregularly squamulose in central parts, with up to 3 mm long and 0.2 mm wide, divergent, sparingly branched marginal lobes, forming up to 1.5 cm wide, stellate rosettes which often die off in the center forming concentric arcs of lobes; lower surface pale, hypothallus absent. Isidia cylindrical, up to 0.3 mm tall and 0.05-0.1 mm thick. Upper surface of lobes with densely packed, parallel hyphae, the photobiont cells mostly concentrated near the surface; central parts of lobes with a more or less well-developed hyphal strand. Apothecia absent in the isidiate form, those of the nominal variety lecanorine, to 0.5 mm across, with a brown disc and thalline margin, the ascospores 1-septate, hyaline, narrowly ellipsoid, 12-15 x 4-5 µm. Photobiont cyanobacterial, Scytonema-like. Spot tests: all negative. Chemistry: without lichen substances.Note: according to Czeika & Czeika (2007) this calcicolous species does not occur in Europe, which led Nimis & al. (2018) to consider it as of dubious occurrence in the Alps, due to possible confusion with the very similar P. posterulum. However, the var. isidiatum has been recently reported from Switzerland (Dietrich 2018), and should be looked for in the Italian Alps. The two species, which are very similar and share the presence of lecanorine apothecia, have been never sequenced, and their distinction needs further study.
Growth form: Crustose placodiomorph
Substrata: rocks
Photobiont: cyanobacteria, filamentous (e.g. Nostoc, Scytonema)
Reproductive strategy: mainly asexual, by isidia, or isidia-like structures (e.g. schizidia)
Poorly known taxon in need of further study
Predictive model
Curtis Randall Björk CC BY-SA 4.0
British Columbia, North Thopmson Valley, Vavenby Date: 2012-02-04 Limestone cliffs on lightly forested, south-facing slope
Curtis Randall Björk – CC BY-SA 4.0
British Columbia, North Thopmson Valley, Vavenby Date: 2012-02-04 Limestone cliffs on lightly forested, south-facing slope
Growth form: Crustose placodiomorph
Substrata: rocks
Photobiont: cyanobacteria, filamentous (e.g. Nostoc, Scytonema)
Reproductive strategy: mainly asexual, by isidia, or isidia-like structures (e.g. schizidia)
Poorly known taxon in need of further study
Predictive model
Curtis Randall Björk CC BY-SA 4.0
British Columbia, North Thopmson Valley, Vavenby Date: 2012-02-04 Limestone cliffs on lightly forested, south-facing slope
