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. 237 The present study is a revision of the shrubby to subpendent species found in East Fennoscandia. Special attention is paid to the identity, biblio- graphic citation, typification and secondary chem- istry of the taxa described from the study area. MATERIAL AND METHODS The study is mainly based on herbarium material, includ- ing numerous type specimens, deposited in BM, H (incl. H- ACH, H-NYL), KPABG, KUO, LBL, OULU (incl. herb. Oulanka), S (incl. S-Motyka), TUR (incl. TUR-V) and UPS. However, not every single specimen in the large collec- tions in H, for instance, was identified. The study also in- cludes field observations. Thickness of the cortex, medulla and central axis were measured by cutting a short segment (usually 1 mm or less) of a branch, and the layers were measured along two crossed sections from both ends of the segment. Measurements were made with a stereomicroscope on the thickest part of the largest branch. For each meas- ured specimen, thicknesses are given as an average of all measurements. The ratio of the width of the cortex, the me- dulla and the central axis, can be given as a percent of the radius for the cortex and the medulla, and as a percent of the diameter for the axis (%C/%M/%A). Because of the sparse material of Usnea diplotypus, its inner structure was studied by the method of Clerc (1984). In this method the branch is cut to the middle point, and the thickness of the layers is measured from a cross section. Chemistry was examined by means of standardized thin-layer chromatog- raphy (TLC), described by Culberson and Ammann (1979), Culberson et al. (1981), and White and James (1985). The author Halonen is responsible for the taxonomy, while the author Myllys has studied the morphology and the chemistry together with the first author. The author Ahti is responsible for the nomenclature together with Halonen, and the author Petrova has studied and collected Usnea spec- imens from the Murmansk Region. MORPHOLOGY According to Clerc (1987a,1987b), the most di- agnostic morphological characters of Usnea are (1) the dominant branching patterns, (2) the shape of the secondary branches, (3) the colour and fre- quency of segmentation of the basal portions, (4) the type of soralia and (5) details of the inner struc- ture. The shape and density of papillae and the density of fibrils are also useful, but are to a con- siderable extent environmentally controlled. In the East Fennoscandian species, the colour of the liv- ing thallus does not have a notable diagnostic value. In contrast, the inner structure seems to have a remarkable systematic significance. The species within the U. florida agg. ( U. fulvoreagens , U. gla- brescens , U. subfloridana and U. wasmuthii ), and within the U. rigida agg. ( U. diplotypus , U. lappo- nica and U. substerilis ) are similar in their anat- omy (Table 1; see also Clerc 1984), while U. gla- brata and U. hirta , which do not belong to either aggregate, differ in their anatomy from the other species. The majority of the East Fennoscandian Usnea species have a shrubby, divergent thallus, which may become subpendent in most species, i.e. hav- ing pendent apical parts. Some of these species may also very rarely be pendent along the entire length of the thallus. The branching pattern is iso- tomic-dichotomous when dividing branches are somewhat equal in thickness, or anisotomic-di- chotomous when they are not. Furthermore, speci- mens with an unusual branching pattern for a spe- cies are not rare. Axils of the thickest branches are Table 1. Thicknesses of the cortex (% of the radius), the medulla (% of the radius) and the central axis (% of the diameter) of the East Fennoscandian shrubby Usnea species. * = thicknesses measured with a method differ- ent from that used for the other species ( see Methods). ————————————————————————————————————————————————— Cortex Medulla Central axis ————————————————————————————————————————————————— Usnea glabrata ( n = 12) 4– 5 –7 32– 36 –39 13– 18 –23 Usnea hirta ( n = 18) 6– 8 –10 19– 27 –32 21– 31 –46 Usnea diplotypus * ( n = 9) 7– 9 –10 17– 22 –26 33– 40 –47 Usnea substerilis ( n = 12) 6– 9 –13 10– 20 –28 31– 42 –54 Usnea lapponica ( n = 42) 4– 9 –12 10– 19 –32 27– 45 –72 Usnea glabrescens ( n = 30) 9– 11 –13 10– 17 –23 32– 43 –56 Usnea fulvoreagens ( n = 28) 8– 11 –15 8– 14 –20 38– 50 –58 Usnea subfloridana ( n = 18) 10– 12 –15 7– 14 –21 32– 47 –66 Usnea wasmuthii ( n = 18) 10– 12 –15 5– 10 –16 44– 55 –65 —————————————————————————————————————————————————