Type. SIBERIA OCCIDENTALI. Konda, ad lignum putridum in pineto prope Leunsk, s.d. E. Vainio s.n. (TUR-V 08798 - holotype!)
Rinodina thujae (H. Magn.) Sheard, Bryologist 90: 164 (1987). Basionym. Rinodina marysvillensis var. thujae H. Magn., Bot. Not. 1953: 192. Type. [U.S.A.] WISCONSIN. Villas Co., Eagle River, on Thuja occidentalis, 1946, J.W. Thomson 2122 (U ‑ holotype!).
Description.Thallus thin, becoming thick, light grey to grey‑green or grey-brown, areolate; areoles discrete, bullate, sometimes developing ascending, sublobate or subsquamulose margins, to 0.15‑0.40 mm wide, or becoming confluent to form a thicker, verrucose thallus, areoles then to ca. 0.50 mm wide; surface shining or matt; margin mostly indeterminate; prothallus sometimes present on smooth bark, dark, fimbriate; vegetative propagules sometimes present; forming a continuous granular to blastidiate surface; blastidia 50-100 x 25-40 µm, disintegrating into soredia to 30-45 µm in diam., concolourous with thallus, or soredia sometimes lighter green and smaller, 20-35 µm in diam.; then often occurring in poorly defined soralia to ca. 0.40 mm in diam. Apothecia quickly becoming narrowly attached, frequent, rarely contiguous, to 0.60-1.00 mm in diam.; disc dark red-brown, becoming black, often lightly pruinose, plane, rarely becoming markedly convex; thalline margin concolourous with thallus, entire becoming flexuose, persistent, 0.05‑0.10 mm wide; excipular ring often quite well developed in mature apothecia, confluent or raised. ApothecialAnatomy. Thalline exciple 65‑115 µm wide laterally; cortex cellular, 10‑20 µm wide; epinecral layer absent; crystals present in cortex, absent in medulla; cortical cells usually not pigmented, to 3.5‑5.5 µm wide; algal cells to 9.5‑16.5 µm long; thalline exciple 80‑125 µm below, cortex to 20‑70 µm wide, hyphae intricate; proper exciple hyaline, 10‑15 µm wide laterally, expanding to 20‑35 µm wide peripherally; hypothecium colourless, 40‑120 µm deep; hymenium 70‑100 µm high, not inspersed; paraphyses ca. 2.0‑2.5 µm wide, not conglutinate, apices expanded to 3.0‑4.5 µm wide, hardly pigmented but immersed in diffuse pigment forming a red‑brown epihymenium, usually with included crystals; asci 50‑80 x 15‑19 µm. Ascospores 8/ascus, Type A development, Physcia‑type, (14.5-)17.0-18.0(-20.5) x (7.0-)9.0-9.5(-11.5) µm, average l/b ratio 1.8-2.0, lumina becoming less angular at maturity, apical wall usually remaining thickened; torus well developed; walls not ornamented. Pycnidia surficial, brown to ca. 0.10 mm in diam.; conidiophores type VI; conidia bacilliform, 3.5-4.5 x 1.5 µm.
Chemistry. Spot tests, K‑ or K+ faint yellow, C-, P+ cinnabar‑orange; secondary metabolites, pannarin in cortex and epihymenium (atranorin erroneously reported by Giralt et al. 1994).
Substrate and Ecology. This corticolous species is relatively uncommon and favours mesic habitats, particularly Thuja swamps. It has been recorded on Abies balsamea, Betula alleghaniensis, B. populifolia, Larix laricina, Picea mariana, Pinus strobus and Thuja occidentalis. Rinodina excrescens has been found accompanied by two other sorediate Rinodina species, R. degeliana and R. efflorescens.
Distribution. Found in the northern part of the Great Lakes region, very rare eastwards to Massachusetts. It has been recorded also from Austria, Croatia and western Siberia in Eurasia (Giralt et al. 1995).
Notes.Rinodina excrescens is well characterized by a thallus which, at least initially, is made up of discrete, bullate areoles and by the presence of pannarin in the cortex and epihymenium. The thallus may sometimes become sorediate. Two other corticolous species in North America, R. efflorescens and R. willeyii, also possess pannarin and are sorediate. Both are distinguished by their plane rather than bullate or verrucose thalli and the presence of zeorin in addition to pannarin.
First recorded for North America as a variety of R. marysvillensis, a west coast species that possesses a continuous rather than a bullate thallus, never develops the large apothecia with flexuose margins, possesses ornamented rather than smooth walled spores, and atranorin rather than pannarin in the thallus. The two species are alike only in their possession of pannarin in the epihymenium and their similar sized spores. Rinodina excrescens of Brodo et al. (1987) was described as a new species, R. thomsonii by Sheard (1995), a species now placed into synonymy with R. santae-monicae from the west coast.
Specimens examined. CANADA. ONTARIO. Gloucester Co., Albion-Leitrim road intersection, P.Y. Wong 4525. QUEBEC. Gatineau Co., Lac Meech, I.M. Brodo 25002 (both CANL). U.S.A. MASSACHUSETTS. Worcester Co., Princeton, P. May 3456 (personal herb.). MICHIGAN. Alger Co., Munising, S.C. Tucker 17023 (LSU); Cheboygan Co., Hebron Mail Road, R.C. Harris 9379 (MICH). MINNESOTA. Becker Co., Missouri Lake, C.M. Wetmore 23798; Beltrami Co., Bemidji, B. Fink 529, 547 (both MIN); 1900, B. Fink (MU, MIN); B. Fink 538 (US); Clearwater Co., Itasca State Park, C.M. Wetmore 26123, 35849; Cook Co., 19 mi N Toft, T.D. Trana 14612; Itasca Co., 20 mi N Grand Rapids, C.M. Wetmore 42203 (all MIN); Highland Lake, B. McCune 19323 (personal herb.); Lake Co., 3 mi W Isabella, C.M. Wetmore 77000; Roseau Co., Warroad, 1901, B. Fink; St. Louis Co., 17 mi NW Ely, T.D. Trana 13449, 13594; Voyageurs Nat. Park, C.M. Wetmore 32864. WISCONSIN. Bayfield Co., Beaver Lake, C.M. Wetmore 71353; Bellevue Lake, C.M. Wetmore 70786; Lee Lake, C.M. Wetmore 71264; NE Anderson Lake, C.M. Wetmore 71479; NW Rainbow Lake, C.M. Wetmore 71083, 71155 (all MIN); Vilas Co., Eagle River, J.W. Thomson 2122, 2130 (UPS, WIS).
Selected References. Magnusson (1947a), Harris (1977 Fig. 162 as Rinodina sp. #2), Brodo (1988 as R. thujae), Giralt et al. (1994), Giralt et al. (1995), Sheard (1995), Thomson (2003).