Parmotrema reticulatum (Taylor) M. Choisy

    Thallus foliose, loosely attached to the substratum, to 15 cm across, lobes 5-15 mm wide, tips rounded and crenulate; upper surface grey-glaucous, pale grey, minutely reticulated, reticulations suggesting minute cracks on old and dry specimen, swollen and capitate soralia at lobe margins, cilia almost absent or then very short and black; lower surface dark brown to black with simple rhizines extending up to the margin. Apothecia very scarce, markedly sessile and almost shortly stipitate, 5-8 mm diam., disc brownish, exciple sorediate.  Ascospores simple, ellipsoid, 13-19 x 8-10 µm. Cortex: C-, KC-, K+ yellow (red after a few minutes and cortex lysis and medulla reaction), Pd+/- yellow ; medulla: C-, KC+ yellow > red, K+ yellow > red, Pd+ red-orange, UV-. Oceanic trends, rather common on tree trunks and also on mossy rocks. Not to be confused with Parmotrema perlatum of which soredia distribution suggests pearl necklace, without rhizine at lobe margins, without reticulum on the lobe upper surface and K+ yellow, nor with Parmotrema arnoldii, which is Pd- and with long black cilia towards lobe margins.

N.B. It was described in 1974 Parmotrema pseudoreticulatum very similar and only distinguishable with certainty by DNA analysis but which differs macroscopically by the absence of rhizines towards the margin of the lobes, thicker and less upturned with on the upper side a less clear network and incomplete or replaced by smudges or stippling, but there seem to be intermediates.