Pannaria streimannii is a tripartite, foliose
Pannaria with broad lobes. The lobe margin is very narrow and recurved, marking the growth zone. Like its close relative
P. howeana, it is only loosely attached to the
substrate because it has few
rhizines. The lower surface shows long, adpressed
hyphae arranged in lengthwise lines that radiate along the branching lobes. The upper surface is partly covered by a sparse , a thin, fuzzy covering. The most conspicuous feature is the abundant . They are semi-erect, typically 0.2 to 1.0 mm wide (occasionally to 2.5 mm), usually round to nearly round, and narrowed at the base. Other ascending lobules were not seen in the type material. Apothecia, the
sexual fruiting bodies, were not observed. In older
herbarium material, the thalli remained pale olive green and did not rapidly shift to violet-brown when rewetted, unlike many other tripartite
Pannaria species. The
green algal cells were described as and unusually small. As with
P. howeana, the reported secondary chemistry includes porphyrilic acid together with vicanicin and leprolomin. ==Habitat and distribution==