Usnea Scabrata

Day 178: With the help of Daphne Fisher Stone's marvelous "aide memoire" to Usneas of the Pacific Northwest, I was able to identify Usnea scabrata, a species which has puzzled me since I lived on one of western Washington's prairies. It is one of several Usneas which occur on Garry Oak (Quercus garryana) in the area from Yelm to Tenino, and arguably dominant on those trees just south of Rainier. It is characterized by a pendulant thallus, the individual strands calling to mind U. longissima, but branching and significantly shorter. In cross-section, the medulla (inner flesh) is quite thick compared to the cortex (outer skin), and the axis (central cord) accounts for almost half the width of the section (the ratio, if you are interested, is C8, M17, A49). The branches are uneven and dented, with papillae and isidia present in most cases. Like U. longissima, there are many fibrils shooting off from the main branches, somewhat like a loosely-spun Christmas garland. Very few annual cracks encircle the branches, and these are not conspicuous. No chemical testing should be necessary to identify the species. Of all the lichens in our woods, the Usneas are perhaps the most graceful and elegant, and they are by far one of the most sensitive, taking offense wherever even minor amounts of pollutants are present in their air. It is refreshing, both literally and figuratively, to place yourself in their company.