Thallus tufted fruticose 6-24 (-65) mm tall, terete or partly flattened, inflated, esore-diate, with few fenestrations, mainly toward the base, pale to dark yellow, the surface smooth, shining; the medulla white, lax in part, hollow in part. Apothecia to 4 mm broad, subterminal or lateral; margin concolorous with the thallus, reverse smooth; disk pale brownish, bare; spores oblong with rounded apices, straight, 2-celled, 11-13 x 4-5 µ. Pycnidia pale.

Reactions: K — , KC—, C— , P— .

Contents: usnic and divaricatic acids.

This species grows on soil or rocks. It is amphi-Beringian, ranging in Siberia and from Alaska to King William Peninsula, N.W.T. Bowler and Rundel (1977) suggest that this is a composite species composed of one element which is a coarse plant on rocks with lateral apothecia, pale pycnidia, and a glossy opaque cortex. The other element is inland, on soil, is much smaller, lacks apothecia and pycnidia, has a translucent cortex and resembles a Cla-donia. Vainio reported that this species might have soredia at the tips. If this occurs this may easily be distinguished from the sorediate R. scoparia by the chemistry, divaricatic acid instead of sekikaic acid aggregate.

Reactions: K— , KC+ , P— .

Contents: sekikaic and homosekikaic and usnic acids in one strain, another contains divaricatic acid.

This species usually grows on twigs, especially of conifers, rarely on cliffs. It is circumpolar, boreal, occurring along the forest border.