Type. U.S.A. MINNESOTA. St. Louis Co., white cedar swamp near Norway Point Picnic Grounds, 6 mi S Hoyt Lakes. Small area of Thuja [occidentalis] with some alder. Sec. 7, T57N, R14W. 12 Sept. 1977, C.M. Wetmore 30889 (holotype MIN, isotype SASK).
Description. Thallus thin, dark grey to ochraceous, continuous becoming rimose, not areolate; surface plane to rugose, matt; margin indeterminate; prothallus absent; vegetative propagules present; consoredia almost covering surface, slightly darker, more brownish than thallus, 35-60 µm wide. Apothecia broadly attached, scattered to frequent, not contiguous, to 0.60-0.65 mm diam.; disc dark brown, plane, quickly becoming black, convex; thalline margin 0.05-0.10 mm wide, sometimes incomplete, quickly becoming excluded; excipular ring absent or raised. ApothecialAnatomy. Thalline exciple 50-60 µm wide laterally; cortex ca. 10 µm wide, poorly differentiated; epinecral layer absent; crystals absent in cortex and medulla; cortical cells to 4.5-5.0 µm wide, not pigmented; algal cells to 13.5-17.0 µm long; thalline exciple absent or 35 µm wide below, cortex then ca. 15 µm deep; proper exciple hyaline, 10-15 µm wide laterally, 30-60 µm wide above; hypothecium colourless or yellowish (yellow pigment, reacting K+ brilliant rose occurs in thallus below this tissue), ca. 100 µm deep in convex apothecia; hymenium 80-110 µm high, not inspersed; paraphyses filaments 2.0-2.5 µm wide, somewhat conglutinate, apices to 5.0-6.0 µm wide, lightly pigmented forming a light brown epihymenium; asci ca. 70 x 22-24 µm. Ascospores 8/ascus, Type A development, Mischoblastia-type, (17.5-) 20.0-21.5(-24.0) x (9.0-)10.5-11.0(-12.5) µm, l/b ratio 1.8-2.0, lumina becoming inflated and more Pachysporaria-like when overmature; torus narrow at maturity; walls not ornamented. Pycnidia not seen.
Chemistry. Spot tests all negative; secondary metabolites absent (Tønsberg, personal communication).
Substrate and Ecology. Corticolous on Tsugaoccidentalis and Fraxinus, possibly limited to mesic habitats.
Distribution. A North American endemic, currently known only from the two counties of extreme northeastern Minnesota.
Notes. The vegetative propagules of the thallus and the convex apothecia are reminiscent of the southern R. colobinoides. The similarity extends to a yellow pigment sometimes present below the apothecium which reacts a K+ brilliant rose-red. However, the spores of R. wetmorei are significantly larger and belong to the Mischoblastia- rather than the Pachysporaria-type.
This species has been described with some hesitation since it is based on only two specimens. However, it is very unusual in being a corticolous species possessing Mischoblastia-type spores. Together with the European R. euskadiensis, it is only the second such species known.
Paraype. U.S.A. MINNESOTA. Lake Co., Superior Nat. Forest, S Little Isabella River Campground, on Fraxinus in ash bog, Sec.T60N R9W, 17 Sept. 1989, C.M. Wetmore 64090 (MIN).