Thallus within the substratum, immersed and not apparent, or crustose, indistinct to clearly visible, thin, edge indefinite, +/- smooth or rimose, pale grey, or yellowish grey to greenish grey, often with distinct bluish pigment. Apothecia occurring singly, or clustered in groups, sessile, or constricted at the base to almost raised, flat when mature or flexuose, 0.4–1.3(–1.4) mm diam.; disc plane, smooth, yellow, pale greenish yellow, or yellow-orange to pale brown, epruinose, or slightly pruinose; margin prominent or level with the disc, often considerably thick, smooth or rough, entire or distinctly crenate, even, uniform, epruinose or pruinose, paler than thallus and paler than disc, often with bluish pigment. Amphithecium 70–170(–270) μm thick, corticate, algae densely filling the area below the cortex; cortex usually distinctly delimited, rarely not distinctly delimited, uniform, or slightly thicker at the base than at the sides, 30–50 μm thick laterally and 50–70 μm thick at the base, composed of adglutinated hyphae to prosoplectenchymatous, obscured by granules occasionally interfering into the area below the cortex (pol+, insoluble in K, soluble in N); parathecium usually distinct, prosoplectenchymatous, 10–30 μm wide; epithecium hyaline or shades of yellow or brown, granular (pol+!), granules superficial and between paraphyses tips, fine to coarse, soluble in K and insoluble in N, sometimes with an epipsamma (insoluble in K, soluble in N); hymenium hyaline, 50–90 μm high; subhymenium indistinct; hypothecium hyaline or distinctly yellow to orange (becoming more intense in K), composed of prosoplectenchyma, clear, without granules, confluent with parathecium and similarin colour, 50–160 μm high. Paraphyses simple or dichotomously branched at tips, slender orthickened, not expanded, or slightly expanded apically, usually not pigmented, free in K. Asci clavate to broadly clavate, 4–8-spored; ascospores hyaline, simple, broadly ellipsoid (broadly ellipsoid to narrowly ellipsoid), 7.5–[10.8]–13 × 4.5–[6.0]–7.5 μm, Q = 1.2–[1.8]–2.6. Pycnidia rare, black, inconspicuous; conidia falcate – consistently filiform and characteristically curved, 10–17(–18) × 1 μm.
CHEMISTRY. Apothecial margin K+ yellow, C– or C+ yellow, KC+ yellow, PD–; disc K+ yellow or orange, C+ yellow or orange, PD–; apothecia UV+ yellow-orange. Lichen products: vinetorin (5-chloro-3-O-methylnorlichexanthone) detected by TLC.
HABITAT. Directly on calcareous rock (limestone, calcium-rich sandstone) and concrete or overgrowing or commensally on other lichens, e.g., Aspicilia calcarea (L.) Mudd, Caloplaca spp., Lecanora spp., Physcia spp., Phaeophyscianigricans (Florke) Moberg, Verrucaria spp.; occasionallyon bark, bryophytes and plant debris,also on metal.
DISTRIBUTION. It is a widespread species in Europe and North America. It is also known from Asia, Australia and New Zeland (sic). In North America it occurs in the Arctic, alpine, boreal and temperate regions with the main distribution in temperate areas.
DISCUSSION.Lecanora semipallida is one of the more distinct species of the L. dispersa complex. A key character distinguishing L. semipallida is the presence of epithecial granules thatare soluble in K. The presence of vinetorin, resultingin positive spot tests and UV reactions ofthe apothecial disc, is also diagnostic. Especiallyinteresting was the discovery of elongate, curvedconidia produced by the species. Morphologically, L. semipallida is a highly variable species. Thesize, shape and colouration of the apothecia mayvary significantly. The species is consistent inregard to anatomy (properties of epithecial granules)and chemistry (vinetorin always present). A closely related species is L. invadens H. Magn,which differs in having a more distinct thallus than L. semipallida, a dark brown to blackish,epruinose or heavily pruinose apothecial disc, and a bluish-green epithecium. For comparison with L. dispersa, see discussion under the species.
NOMENCLATURAL NOTES.Lecanora semipallida H. Magn. was shown to be the correct name for the common, widespread member of the L. dispersa complex hitherto known as L. flotoviana (auct. non Spreng.). Further, L. xanthostoma Cl. Roux was shown to be conspecificwith L. semipallida and therefore was relegated tosynonymy (Åliwa 2007). Full details on the statusand application of the names are provided in thepublication.
Thallus: within substrate, not visible, or crustose, indistinct to clearly visible, thin, ecorticate surface: if present, pale gray, or yellowish gray to greenish gray, often with distinct bluish pigment, esorediate Apothecia: occurring singly, or clustered in groups, sessile, or constricted at base to almost raised, flat when mature, 0.4-1.3 mm in diam. disc: shades of yellow, pale greenish yellow, or yellow-orange to pale brown, epruinose, or slightly pruinose, smooth, usually without an epipsamma amphithecium: present, with algae filling the medulla, with gelatinous hyphae obscured by granules (pol+, insoluble in K, soluble in N), 70-170 µm thick, corticate; cortex: usually distinctly delimited, rarely not distinctly delimited, uniform, or slightly thicker at the base than at the sides, 30-50 µm thick laterally and 50-70 µm thick at base parathecium: usually distinct, prosoplectenchymatous, 10-30 µm wide epihymenium: hyaline or shades of yellow or brown, granular (pol+), granules superficial and between paraphyses tips, coarse, soluble in K and insoluble in N hymenium: hyaline, 50-70 µm tall; paraphyses: simple or branched at tips, slender or thickened, not expanded, or slightly expanded at top, usually not pigmented, free in K; subhymenium: indistinct; hypothecium: hyaline or distinctly yellow to orange (turning more intense in K), composed of prosoplectenchyma, clear, without granules, confluent with proper margin and similar in color, 50-150 µm thick asci: clavate, 4-8-spored ascospores: hyaline, simple, ellipsoid, 8.9-11.8 x 4.5-5.9(-7.4) µm Pycnidia: rare, black, inconspicuous conidia: elongate, filiform, usually curved, 15-18 µm long Spot tests: apothecial margin K+ yellow, C- or C+ yellow, KC- or KC+ yellow, P-; disc K+ yellow or orange, C+ yellow or orange, P-; apothecia UV+ yellow-orange Secondary metabolites: vinetorin (5-chloro-3-O-methylnorlichexanthone). Substrate and ecology: directly on calcareous rocks (limestone, sandstone) or overgrowing other lichens, occasionally on bark World distribution: known from North America, Europe and Antarctica, probably a cosmopolitan species Sonoran distribution: southern and northern Arizona. Notes: The species is distinguished from the other members of L. dispersa group by its C+ and K+ reactions of apothecial discs, which are also UV+ yellow to orange. The epihymenial granules soluble in K and broadly ellipsoid spores are also characteristic. Although L. flotoviana represents distinctive species, it was poorly known and hithero misinterpreted. Due to its considerable morphological variability, it is very likely that the taxon was described several times. Lecanora flotoviana was recognized for the first time for North America by R.C. Harris. In the literature the alternative spelling L. flotowiana is often used. However, on the basis of article 60.7 in the Botanical Code, the Latinized spelling, L. flotoviana, must be used because this was clearly the intention of Sprengel, who consistently used the Latin spelling throughout his publication, which was entirely written in Latin.