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. 253 strain 1. Republic of Karelia. Karelia ladogensis: Kurkijoki, Vossina, 1936 Räsänen (H), strain 1. Karelia onegensis: ca. 7 km W of Medvezhyegorsk, 1942 Laurila (H), strain 4. 9. Usnea wasmuthii Räsänen Ann. Acad. Sci. Fenn., Ser. A4, 34(4): 19. 1931. — Type: Estonia. Harjumaa, Tallinn, Kakumäe (Kakkomägi), Picea , 1908 Wasmuth (H!, holotype), fertile, %C/%M/%A: 11/12/ 53, upper left-hand specimen. Chemistry: usnic and barbatic acids. Usnea glabrescens (Nyl. ex Vain.) Vain. ex Räsänen var. sanguinea Räsänen, Acta Fauna Fl. Universali, Ser. 2, Bot., 2(1): 3. 1935. —Type: Romania. Distr. Gorj, Mt. Cioclovina, ad ram. Fagi silvatici , 1933 Cretzoiu (H!, holotype?). Chemis- try: usnic, salazinic, barbatic and 4- O -demethylbarbatic acids. Thallus erect to rarely subpendent, to ca. 10(–13) cm long, usually quite richly branched. Branchingmostly isotomic-dichotomous. Branches slender, to ca. 1(–1.5) mm in diam. Annular cracks sparse to relatively abundant, quite often with white medullary rings. Base distinctly blackened, often with ± numerous longitudinal cracks (Fig. 8). Cortex relatively thick, 10– 12 –15% ( n = 18). Medulla dense, thin to relatively thin, 5– 10 –16% ( n = 18). Central axis usually thick, 44– 55 –65% ( n = 18). Papillae small and verrucous, more rarely cylindric, normally fairly densely arranged. Fi- brils relatively sparse to abundant, usually not present near apical parts. Soralia ( see Clerc 1987b: 101) tuberculate to often slightly excavate and ± elongated (especially near apices), minute to en- larged, developing from plane cortex or from tu- bercles; soredia farinose. Isidia short but often absent on mature soralia. Chemistry . Strain 1 ( n = 29): usnic + barbatic ± 4- O -demethylbarbatic ± protocetraric (trace) acids (K–, PD–); strain 2 ( n = 8): usnic + salazinic + barbatic ± 4- O -demethylbarbatic ± protocetraric (trace) acids (K+ yellow, orange or red, PD+ yel- low or orange); strain 3 ( n = 2): usnic + salazinic acids (K+ orange or red, PD+ yellow or orange); strain 4 ( n = 1): usnic acid (K–, PD–). Strain 2 has eastern tendencies in East Fennoscandia since we have seen only two specimens from western Fin- land (Varsinais-Suomi: Kemiö, and Oulun Poh- janmaa: Oulu). According to Krog et al. (1994), strain 1 is rare in Norway. Bystrek et al. (1981) described Usnea wasmuthii f. negativa Bystrek for a chemotype in Poland (type specimen not seen) which reacts K– and PD–. However, these colour reactions are typical for the type strain. Remarks . Usnea wasmuthii is closely related to U. subfloridana ( see the comments under the latter species). Ecology . The species has been collected main- ly from Alnus ( n = 8), Betula ( n = 7), Sorbus ( n = 5) and Picea ( n = 4), and less frequently from Quercus , Salix , Populus , Malus , Larix , Juniperus and lignum (in total 36 specimens). Usnea was- muthii is most common in moderately open mixed forests and it occurs often in inhabited areas. Distribution . Finland: 1–3, 6, 9–11, 13–15, 17, 19; Russia: 2, 3, 6. World distribution: northern boreal to temperate. The species has been found in Eurasia (Motyka 1936) and recently in North America (Halonen 2000), though Halonen et al. (1998) rejected some earlier North American re- cords. Usnea wasmuthii is rare to scattered in southern parts of East Fennoscandia and very rare in northern Finland (Fig. 9). The species will be added to the list of threatened lichens of Finland Fig. 8. Longitudinal cracks at the blackened base of Usnea wasmuthii Räsänen. Two annular cracks are pointed by arrows. From 1946 Railonsala (OULU). Scale = 0.5 mm.