Gyalecta truncigena
≡Gyalecta wahlenbergiana β truncigena Ach., Lichenogr. universalis: 152 (1810).
Description : Thallus inconspicuous, thin to scurfy, encrusting bark, glaucous greenish or greyish, slightly powdery. Apothecia 0.2–0.5 mm diam., immersed in bark, rarely superficial, scattered to crowded–confluent; proper exciple thick, smooth, even or crenulate, cream to brownish or yellow-pink; disc pale-orange, pinkish to pale-brown. Ascospores ellipsoidal, ovoid or oblong-fusiform, sparingly muriform, septa oblique, rarely regularly transverse, 14–28(–31) × 5–9 μm.
Chemistry : TLC−, all reactions negative.
S: On nutrient-rich bark of rough-barked, deciduous, wayside trees, Ulmus, Fraxinus, Quercus etc., in well-lit habitats. Very easily overlooked. Widespread in the Northern Hemisphere (Purvis et al. 1992; Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Nimis & Martellos 2003; Ryan & Nimis 2004a; Santesson et al. 2004).
?Cosmopolitan
Illustrations : James & Woods (1992a: 260, fig. 14B); Dobson (1992: 150; 2000: 164); Boqueras (2000: 194, fig. 28D).
Gyalecta truncigena is characterised by: the corticolous habit; the inconspicuous thallus; Trentepohlia photobiont (shows orange when fresh material is scratched); immersed or semi-immersed, pale apothecia; colourless, ellipsoidal to oblong-fusiform, submuriform ascospores, 14–28(–31) × 5–9 μm.
