Hypogymnia physodes is a small to medium foliose lichen measuring 2 to 10cm in diameter with a highly branched, though compact, thallus. Like other Hypogymnia species, the light color of the upper thallus surface contrasts sharply with lower black surface. The color of the upper thallus surface can vary from light green to gray and is typically smooth. Also indicative of the genus, is the lack of rhizines on the lower surface. The hollow lobes of the thallus are less than 2mm wide and appressed to the substrate surface with only the tips being free. Helping to distinguish H. physodes from other Hypogymnia species, the upper interior surface of the lobes is white with a dark lower interior surface. The asexual reproductive propagules, soredia, are produced on the inside of the lobe tips that appear to break open in the shape of lips, a diagnostic characteristic of the species. Sexual apothecia are rarely observed.
The typical habitat includes open to slightly shaded sites in low to mid elevation forests in addition to non forested regions such as steppe and shrub thickets, of both urban and suburban areas. H. physodes uses bark and wood of deciduous and coniferous trees as a primary subsrate, only sometimes found on rocks or moss covering rocks. It has been found, though rarely in tundra sod.
This species is common throughout the Pacific Northwest as well as the northern hemisphere.
H. physodes is one of the most pollution tolerant lichen species, commonly observed in city parks and populated areas. In Europe H. physodes has been studied as an air quality indicator since significant concentrations of sulfur dioxide will eventually kill this resilient species.
Historically, lichens haven’t been used in daily life as extensively as plants though the Potawatomi Indian put H. physodes in soup and eaten as a remedy for constipation and in Scandinavia it was used to make a brown wool dye.
The common names listed for H. physodes include Monk’s Hood Lichen, Hooded Bone Lichen, Puffed Lichen and Hooded Tube Lichen.
Brodo, I.M., S.D. Sharnoff and S. Sharnoff (2001) Lichens of North America. Yale University Press, New Haven, Connecticut.
Kozloff, E.N. (1976) Plants and Animals of the Pacific Northwest. University of Washington Press, Seattle and London.
McCune, B. and L. Geiser (2009) Macrolichens of the Pacific Northwest. Oregon State University Press, Corvallis, Oregon.
Pojar, J. and A. McKinnon (1994) Plants of the Pacific Northwest Coast. Lone Pine Publishing, Washington, Canada.