Petrova O. The lichen genus Usnea in eastern Gennoscandia. III Shrubby species. Ann. Bot. Fennici. 1999, 36, p. 235-256.

ANN. BOT. FENNICI 36 (1999) • Usnea in East Fennoscandia. III. 243 not give any medullary colour reactions with the K reagent). It is notable that four of the five speci- mens containing diffractaic acid have been col- lected from the Lake Ladoga area in Russia. Clerc (1992) did not detect salazinic acid in U. fulvorea- gens in the British Isles, but diffractaic acid seems to be more common there than in East Fennoscan- dia. Remarks . The name Usnea fulvoreagens is in- correct for this species, because the lectotype rep- resents U. subfloridana . Unfortunately, two syn- types have disappeared. The type indicated by Motyka (1936: 284) and Clerc (1987a: 494) is not a type, since it is not cited in the protologue. The authors of the type are also cited incorrectly as “(Räsänen) Motyka” byMotyka. The name is well established, however, and therefore we propose a new conserved type for U. glabrescens var. fulvo- reagens (P. Halonen & T. Ahti unpubl.). The species probably belongs to the same ag- gregate with Usnea glabrescens , U. subfloridana and U. wasmuthii , in which U. florida is the pri- mary fertile species. Usnea florida agg. is charac- terized by the usually isotomic-dichotomous branching pattern, cylindric and tapering branches rarely with foveoles, relatively thick cortex, usu- ally dense medulla, distinctly blackened base and copious papillae. The chemistry of the aggregate is very variable and most of the species have oce- anic tendencies in their distribution. Usnea fulvoreagens is closely related to U. gla- brescens , but is distinguished by the usually small- er, more divergent thallus, normally more abun- dant branches and fibrils, often taller papillae and soralia that are ± confluent and deeply excavate when mature. Furthermore, annular cracks with thick white medullary rings are more common in U. fulvoreagens , and the species only rarely pro- duces salazinic acid, which is very often present in U. glabrescens . The delimitation of U. fulvorea- gens and U. glabrescens can be difficult, how- ever, and intermediate morphs are found (see also Halonen et al. 1998). As pointed out by Clerc (1992), Usnea lapponica , which also has deeply excavate soralia, is formerly often regarded as a synonym of U. fulvoreagens . Usnea lapponica differs, for instance, by its usually anisotomic branching pattern, thicker medulla and different chemistry without the stictic acid group. Ecology . The species has mainly been col- lected from Alnus (35%), Betula (18%), Picea (13%), Sorbus (12%) and Populus (12%), and less frequently from Prunus , Pinus , Salix , Juniperus , Tilia and rocks (in total 96 specimens). Usnea fulvoreagens is likely to be most common in mod- erately open and humid mixed forests, and often occurs close to farmlands or other inhabited ar- eas. The primary phorophytes are second-growth forest species. Distribution . Finland: 1–7, 9–13, 15, 16; Rus- sia: 2–4, 8. World distribution: Europe (Clerc 1992) and western North America (P. Halonen & L. Geiser unpubl.), with oceanic tendencies. The world distribution, however, is still poorly known. Usnea fulvoreagens is rare to scattered in East Fennoscandia with a relatively southern, i.e. mid- dle to southern boreal distribution. The species has been collected more frequently in the inland lake area than in the coastal regions and it is dis- tinctly less common than U. glabrescens . Selected specimens examined . — Finland . Åland: Eckerö, 1935 Räsänen (H), strain 1. Etelä-Karjala: Vehka- lahti, Pyhältö, 1947 Fagerström (H), strain 1. Satakunta: Eura, Kauttua, 1946 Klingstedt (H), strain 1. Etelä-Häme: Fig. 3. Annular cracks with white medullary rings on branches of Usnea fulvoreagens (Räsänen) Räsänen. From 1944 Fagerström (H). Scale = 1 mm.