Montana Field Guide

Thallus foliose, suberect to drooping off the substrate, to 10(15) cm long; lobes mostly 1-3(5) mm broad (occasionally broader in basal parts); upper surface whitish, grayish, pale greenish gray, or browned in exposed sites; lower surface black, brown, white, or with patches of these colors; rhizines few; isidia present mainly on the lobe margins; and apothecia rare McCune and Geiser 2009. Chemistry: Cortex K+ yellow; Medulla K-, C-, KC-, and P- McCune and Geiser 2009.

Large individuals are easily identified by the elongate, narrow lobes with marginal isidia. Some specimens can be similar to those forms of P. glauca that have narrow lobes; one must separate them by the type of asexual reproduction. P. glauca has either soredia or a combination of soredia and isidia while P. herrei has only true isidia (covered with a cortex and therefore shiny) McCune and Geiser 2009.

Generally on conifer bark or wood in low elevation, mesic forests.

Reproduces asexually by isidia.

None identified.